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 $176.67   9.841%   $194.0561   $194.06   $194.05   $194.10  
  Purchase #2 $68.97   11.109%   $76.6319   $76.63   $76.65   $76.60  
  Purchase #3 $117.29   5.242%   $123.4383   $123.44   $123.45   $123.40  
  Purchase #4 $99.86   9.251%   $109.098   $109.10   $109.10   $109.10  
  Purchase #5 $93.85   9.252%   $102.533   $102.53   $102.55   $102.50  
  Purchase #6 $178.48   13.383%   $202.366   $202.37   $202.35   $202.40  
  Purchase #7 $67.80   11.366%   $75.5061   $75.51   $75.50   $75.50  
  7 purchase totals = $802.92       $883.6294   $883.64   $883.65   $883.60