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 $207.95   11.814%   $232.5172   $232.52   $232.50   $232.50  
  Purchase #2 $23.28   8.222%   $25.1941   $25.19   $25.20   $25.20  
  Purchase #3 $224.29   4.399%   $234.1565   $234.16   $234.15   $234.20  
  Purchase #4 $200.77   10.140%   $221.1281   $221.13   $221.15   $221.10  
  Purchase #5 $119.82   6.167%   $127.2093   $127.21   $127.20   $127.20  
  Purchase #6 $63.48   6.625%   $67.6856   $67.69   $67.70   $67.70  
  Purchase #7 $112.88   3.145%   $116.4301   $116.43   $116.45   $116.40  
  7 purchase totals = $952.47       $1,024.3209   $1,024.33   $1,024.35   $1,024.30