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 $58.96   10.774%   $65.3124   $65.31   $65.30   $65.30  
  Purchase #2 $118.60   13.608%   $134.7391   $134.74   $134.75   $134.70  
  Purchase #3 $213.71   10.129%   $235.3567   $235.36   $235.35   $235.40  
  Purchase #4 $194.54   7.810%   $209.7336   $209.73   $209.75   $209.70  
  Purchase #5 $94.42   8.523%   $102.4674   $102.47   $102.45   $102.50  
  Purchase #6 $119.78   3.474%   $123.9412   $123.94   $123.95   $123.90  
  Purchase #7 $48.75   13.118%   $55.145   $55.15   $55.15   $55.10  
  7 purchase totals = $848.76       $926.6954   $926.70   $926.70   $926.60