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 $63.68   5.487%   $67.1741   $67.17   $67.15   $67.20  
  Purchase #2 $202.76   9.687%   $222.4014   $222.40   $222.40   $222.40  
  Purchase #3 $212.54   11.677%   $237.3583   $237.36   $237.35   $237.40  
  Purchase #4 $164.53   3.534%   $170.3445   $170.34   $170.35   $170.30  
  Purchase #5 $9.83   5.719%   $10.3922   $10.39   $10.40   $10.40  
  Purchase #6 $193.52   10.290%   $213.4332   $213.43   $213.45   $213.40  
  Purchase #7 $94.98   6.444%   $101.1005   $101.10   $101.10   $101.10  
  7 purchase totals = $941.84       $1,022.2042   $1,022.19   $1,022.20   $1,022.20