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 $56.82   9.252%   $62.077   $62.08   $62.10   $62.10  
  Purchase #2 $65.50   12.660%   $73.7923   $73.79   $73.80   $73.80  
  Purchase #3 $232.70   13.352%   $263.7701   $263.77   $263.75   $263.80  
  Purchase #4 $214.59   9.614%   $235.2207   $235.22   $235.20   $235.20  
  Purchase #5 $158.89   6.600%   $169.3767   $169.38   $169.40   $169.40  
  Purchase #6 $245.93   10.552%   $271.8805   $271.88   $271.90   $271.90  
  Purchase #7 $176.33   7.263%   $189.1368   $189.14   $189.15   $189.10  
  7 purchase totals = $1,150.76       $1,265.2541   $1,265.26   $1,265.30   $1,265.30