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 $218.47   6.343%   $232.3276   $232.33   $232.35   $232.30  
  Purchase #2 $210.26   12.168%   $235.8444   $235.84   $235.85   $235.80  
  Purchase #3 $47.93   13.625%   $54.4605   $54.46   $54.45   $54.50  
  Purchase #4 $163.73   5.267%   $172.3537   $172.35   $172.35   $172.40  
  Purchase #5 $248.84   3.549%   $257.6713   $257.67   $257.65   $257.70  
  Purchase #6 $197.45   4.630%   $206.5919   $206.59   $206.60   $206.60  
  Purchase #7 $199.82   8.841%   $217.4861   $217.49   $217.50   $217.50  
  7 purchase totals = $1,286.50       $1,376.7355   $1,376.73   $1,376.75   $1,376.80