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 $86.79   10.437%   $95.8483   $95.85   $95.85   $95.80  
  Purchase #2 $236.54   12.244%   $265.502   $265.50   $265.50   $265.50  
  Purchase #3 $227.49   7.700%   $245.0067   $245.01   $245.00   $245.00  
  Purchase #4 $19.41   3.785%   $20.1447   $20.14   $20.15   $20.10  
  Purchase #5 $152.75   13.637%   $173.5805   $173.58   $173.60   $173.60  
  Purchase #6 $156.93   8.781%   $170.71   $170.71   $170.70   $170.70  
  Purchase #7 $94.35   8.653%   $102.5141   $102.51   $102.50   $102.50  
  7 purchase totals = $974.26       $1,073.3063   $1,073.30   $1,073.30   $1,073.20