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 $88.61   11.439%   $98.7461   $98.75   $98.75   $98.70  
  Purchase #2 $126.98   13.139%   $143.6639   $143.66   $143.65   $143.70  
  Purchase #3 $94.60   4.841%   $99.1796   $99.18   $99.20   $99.20  
  Purchase #4 $225.48   6.224%   $239.5139   $239.51   $239.50   $239.50  
  Purchase #5 $43.98   8.572%   $47.75   $47.75   $47.75   $47.80  
  Purchase #6 $123.43   7.753%   $132.9995   $133.00   $133.00   $133.00  
  Purchase #7 $166.81   11.139%   $185.391   $185.39   $185.40   $185.40  
  7 purchase totals = $869.89       $947.2440   $947.24   $947.25   $947.30