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 $224.75   3.761%   $233.2028   $233.20   $233.20   $233.20  
  Purchase #2 $228.61   3.612%   $236.8674   $236.87   $236.85   $236.90  
  Purchase #3 $116.31   7.554%   $125.0961   $125.10   $125.10   $125.10  
  Purchase #4 $26.43   9.803%   $29.0209   $29.02   $29.00   $29.00  
  Purchase #5 $85.77   13.614%   $97.4467   $97.45   $97.45   $97.40  
  Purchase #6 $246.68   8.211%   $266.9349   $266.93   $266.95   $266.90  
  Purchase #7 $233.93   4.251%   $243.8744   $243.87   $243.85   $243.90  
  7 purchase totals = $1,162.48       $1,232.4432   $1,232.44   $1,232.40   $1,232.40