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 $84.55   13.231%   $95.7368   $95.74   $95.75   $95.70  
  Purchase #2 $135.89   8.267%   $147.124   $147.12   $147.10   $147.10  
  Purchase #3 $60.57   8.441%   $65.6827   $65.68   $65.70   $65.70  
  Purchase #4 $78.71   8.843%   $85.6703   $85.67   $85.65   $85.70  
  Purchase #5 $69.76   6.218%   $74.0977   $74.10   $74.10   $74.10  
  Purchase #6 $171.99   13.434%   $195.0951   $195.10   $195.10   $195.10  
  Purchase #7 $244.60   3.199%   $252.4248   $252.42   $252.40   $252.40  
  7 purchase totals = $846.07       $915.8314   $915.83   $915.80   $915.80