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 $92.55   3.275%   $95.581   $95.58   $95.60   $95.60  
  Purchase #2 $148.71   6.567%   $158.4758   $158.48   $158.50   $158.50  
  Purchase #3 $88.84   4.590%   $92.9178   $92.92   $92.90   $92.90  
  Purchase #4 $244.62   7.237%   $262.3231   $262.32   $262.30   $262.30  
  Purchase #5 $59.37   13.165%   $67.1861   $67.19   $67.20   $67.20  
  Purchase #6 $87.63   13.816%   $99.737   $99.74   $99.75   $99.70  
  Purchase #7 $5.40   12.502%   $6.0751   $6.08   $6.10   $6.10  
  7 purchase totals = $727.12       $782.2959   $782.31   $782.35   $782.30