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 $92.53   9.854%   $101.6479   $101.65   $101.65   $101.60  
  Purchase #2 $146.98   11.310%   $163.6034   $163.60   $163.60   $163.60  
  Purchase #3 $76.67   11.106%   $85.185   $85.19   $85.20   $85.20  
  Purchase #4 $241.91   5.743%   $255.8029   $255.80   $255.80   $255.80  
  Purchase #5 $58.42   13.645%   $66.3914   $66.39   $66.40   $66.40  
  Purchase #6 $126.48   6.841%   $135.1325   $135.13   $135.15   $135.10  
  Purchase #7 $118.33   7.494%   $127.1977   $127.20   $127.20   $127.20  
  7 purchase totals = $861.32       $934.9608   $934.96   $935.00   $934.90