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 $190.54   10.725%   $210.9754   $210.98   $211.00   $211.00  
  Purchase #2 $247.79   6.148%   $263.0241   $263.02   $263.00   $263.00  
  Purchase #3 $132.30   13.777%   $150.527   $150.53   $150.55   $150.50  
  Purchase #4 $74.68   11.515%   $83.2794   $83.28   $83.30   $83.30  
  Purchase #5 $79.83   6.419%   $84.9543   $84.95   $84.95   $85.00  
  Purchase #6 $182.85   13.342%   $207.2458   $207.25   $207.25   $207.20  
  Purchase #7 $138.71   10.642%   $153.4715   $153.47   $153.45   $153.50  
  7 purchase totals = $1,046.70       $1,153.4775   $1,153.48   $1,153.50   $1,153.50