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 $115.57   8.246%   $125.0999   $125.10   $125.10   $125.10  
  Purchase #2 $218.59   8.331%   $236.8007   $236.80   $236.80   $236.80  
  Purchase #3 $112.73   6.395%   $119.9391   $119.94   $119.95   $119.90  
  Purchase #4 $162.57   9.761%   $178.4385   $178.44   $178.45   $178.40  
  Purchase #5 $133.96   11.788%   $149.7512   $149.75   $149.75   $149.80  
  Purchase #6 $247.38   7.435%   $265.7727   $265.77   $265.75   $265.80  
  Purchase #7 $120.85   4.801%   $126.652   $126.65   $126.65   $126.70  
  7 purchase totals = $1,111.65       $1,202.4541   $1,202.45   $1,202.45   $1,202.50