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 $119.52   5.785%   $126.4342   $126.43   $126.45   $126.40  
  Purchase #2 $213.53   7.700%   $229.9718   $229.97   $229.95   $230.00  
  Purchase #3 $58.44   10.772%   $64.7352   $64.74   $64.75   $64.70  
  Purchase #4 $189.56   4.191%   $197.5045   $197.50   $197.50   $197.50  
  Purchase #5 $159.64   11.180%   $177.4878   $177.49   $177.50   $177.50  
  Purchase #6 $219.80   6.648%   $234.4123   $234.41   $234.40   $234.40  
  Purchase #7 $156.53   8.441%   $169.7427   $169.74   $169.75   $169.70  
  7 purchase totals = $1,117.02       $1,200.2885   $1,200.28   $1,200.30   $1,200.20