Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $168.28   7.737%   $181.2998   $181.30   $181.30   $181.30  
  Purchase #2 $200.84   11.398%   $223.7317   $223.73   $223.75   $223.70  
  Purchase #3 $179.71   4.221%   $187.2956   $187.30   $187.30   $187.30  
  Purchase #4 $236.57   6.223%   $251.2918   $251.29   $251.30   $251.30  
  Purchase #5 $223.43   7.164%   $239.4365   $239.44   $239.45   $239.40  
  Purchase #6 $218.27   6.585%   $232.6431   $232.64   $232.65   $232.60  
  Purchase #7 $136.47   5.680%   $144.2215   $144.22   $144.20   $144.20  
  7 purchase totals = $1,363.57       $1,459.9200   $1,459.92   $1,459.95   $1,459.80