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 $57.69   9.331%   $63.0731   $63.07   $63.05   $63.10  
  Purchase #2 $210.29   11.522%   $234.5196   $234.52   $234.50   $234.50  
  Purchase #3 $64.47   5.451%   $67.9843   $67.98   $68.00   $68.00  
  Purchase #4 $188.77   8.581%   $204.9684   $204.97   $204.95   $205.00  
  Purchase #5 $127.26   6.488%   $135.5166   $135.52   $135.50   $135.50  
  Purchase #6 $204.96   9.671%   $224.7817   $224.78   $224.80   $224.80  
  Purchase #7 $185.99   4.358%   $194.0954   $194.10   $194.10   $194.10  
  7 purchase totals = $1,039.43       $1,124.9391   $1,124.94   $1,124.90   $1,125.00