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 $92.61   5.818%   $97.998   $98.00   $98.00   $98.00  
  Purchase #2 $93.36   13.550%   $106.0103   $106.01   $106.00   $106.00  
  Purchase #3 $64.65   3.821%   $67.1203   $67.12   $67.10   $67.10  
  Purchase #4 $215.44   11.131%   $239.4206   $239.42   $239.40   $239.40  
  Purchase #5 $149.76   7.304%   $160.6985   $160.70   $160.70   $160.70  
  Purchase #6 $40.63   10.521%   $44.9047   $44.90   $44.90   $44.90  
  Purchase #7 $35.33   5.562%   $37.2951   $37.30   $37.30   $37.30  
  7 purchase totals = $691.78       $753.4475   $753.45   $753.40   $753.40