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 $83.93   12.690%   $94.5807   $94.58   $94.60   $94.60  
  Purchase #2 $76.98   4.667%   $80.5727   $80.57   $80.55   $80.60  
  Purchase #3 $177.77   11.570%   $198.338   $198.34   $198.35   $198.30  
  Purchase #4 $192.53   7.153%   $206.3017   $206.30   $206.30   $206.30  
  Purchase #5 $220.69   5.118%   $231.9849   $231.98   $232.00   $232.00  
  Purchase #6 $165.81   6.610%   $176.77   $176.77   $176.75   $176.80  
  Purchase #7 $27.90   3.232%   $28.8017   $28.80   $28.80   $28.80  
  7 purchase totals = $945.61       $1,017.3497   $1,017.34   $1,017.35   $1,017.40