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 $77.58   10.409%   $85.6553   $85.66   $85.65   $85.70  
  Purchase #2 $230.95   6.843%   $246.7539   $246.75   $246.75   $246.80  
  Purchase #3 $101.96   8.716%   $110.8468   $110.85   $110.85   $110.80  
  Purchase #4 $148.81   3.724%   $154.3517   $154.35   $154.35   $154.40  
  Purchase #5 $202.67   5.343%   $213.4987   $213.50   $213.50   $213.50  
  Purchase #6 $148.56   6.359%   $158.0069   $158.01   $158.00   $158.00  
  Purchase #7 $63.79   7.386%   $68.5015   $68.50   $68.50   $68.50  
  7 purchase totals = $974.32       $1,037.6148   $1,037.62   $1,037.60   $1,037.70