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 $68.52   8.231%   $74.1599   $74.16   $74.15   $74.20  
  Purchase #2 $249.81   4.285%   $260.5144   $260.51   $260.50   $260.50  
  Purchase #3 $116.60   13.179%   $131.9667   $131.97   $131.95   $132.00  
  Purchase #4 $147.54   7.478%   $158.573   $158.57   $158.55   $158.60  
  Purchase #5 $95.73   11.198%   $106.4498   $106.45   $106.45   $106.40  
  Purchase #6 $231.63   9.301%   $253.1739   $253.17   $253.15   $253.20  
  Purchase #7 $228.93   8.153%   $247.5947   $247.59   $247.60   $247.60  
  7 purchase totals = $1,138.76       $1,232.4324   $1,232.42   $1,232.35   $1,232.50