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 $87.58   9.203%   $95.64   $95.64   $95.65   $95.60  
  Purchase #2 $39.84   4.804%   $41.7539   $41.75   $41.75   $41.80  
  Purchase #3 $98.75   3.819%   $102.5213   $102.52   $102.50   $102.50  
  Purchase #4 $225.35   7.583%   $242.4383   $242.44   $242.45   $242.40  
  Purchase #5 $157.98   4.674%   $165.364   $165.36   $165.35   $165.40  
  Purchase #6 $180.56   4.757%   $189.1492   $189.15   $189.15   $189.10  
  Purchase #7 $162.70   6.719%   $173.6318   $173.63   $173.65   $173.60  
  7 purchase totals = $952.76       $1,010.4985   $1,010.49   $1,010.50   $1,010.40