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 $57.28   9.412%   $62.6712   $62.67   $62.65   $62.70  
  Purchase #2 $209.29   11.221%   $232.7744   $232.77   $232.75   $232.80  
  Purchase #3 $177.50   4.529%   $185.539   $185.54   $185.55   $185.50  
  Purchase #4 $8.99   13.422%   $10.1966   $10.20   $10.20   $10.20  
  Purchase #5 $44.46   8.267%   $48.1355   $48.14   $48.15   $48.10  
  Purchase #6 $65.88   12.290%   $73.9767   $73.98   $74.00   $74.00  
  Purchase #7 $11.54   13.131%   $13.0553   $13.06   $13.05   $13.10  
  7 purchase totals = $574.94       $626.3487   $626.36   $626.35   $626.40