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 $88.26   7.802%   $95.146   $95.15   $95.15   $95.10  
  Purchase #2 $146.96   4.361%   $153.3689   $153.37   $153.35   $153.40  
  Purchase #3 $102.36   10.468%   $113.075   $113.08   $113.10   $113.10  
  Purchase #4 $25.84   3.512%   $26.7475   $26.75   $26.75   $26.70  
  Purchase #5 $98.36   12.365%   $110.5222   $110.52   $110.50   $110.50  
  Purchase #6 $140.50   12.546%   $158.1271   $158.13   $158.15   $158.10  
  Purchase #7 $22.37   7.410%   $24.0276   $24.03   $24.05   $24.00  
  7 purchase totals = $624.65       $681.0143   $681.03   $681.05   $680.90