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 $65.26   11.667%   $72.8739   $72.87   $72.85   $72.90  
  Purchase #2 $161.95   12.129%   $181.5929   $181.59   $181.60   $181.60  
  Purchase #3 $20.89   8.162%   $22.595   $22.60   $22.60   $22.60  
  Purchase #4 $213.72   10.472%   $236.1008   $236.10   $236.10   $236.10  
  Purchase #5 $230.74   13.683%   $262.3122   $262.31   $262.30   $262.30  
  Purchase #6 $216.80   6.566%   $231.0351   $231.04   $231.05   $231.00  
  Purchase #7 $161.43   10.370%   $178.1703   $178.17   $178.15   $178.20  
  7 purchase totals = $1,070.79       $1,184.6802   $1,184.68   $1,184.65   $1,184.70