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 $201.39   7.608%   $216.7118   $216.71   $216.70   $216.70  
  Purchase #2 $185.71   12.566%   $209.0463   $209.05   $209.05   $209.00  
  Purchase #3 $182.45   11.859%   $204.0867   $204.09   $204.10   $204.10  
  Purchase #4 $235.52   10.794%   $260.942   $260.94   $260.95   $260.90  
  Purchase #5 $86.73   6.787%   $92.6164   $92.62   $92.60   $92.60  
  Purchase #6 $250.77   10.127%   $276.1655   $276.17   $276.15   $276.20  
  Purchase #7 $203.56   6.771%   $217.343   $217.34   $217.35   $217.30  
  7 purchase totals = $1,346.13       $1,476.9117   $1,476.92   $1,476.90   $1,476.80