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 $88.35   8.302%   $95.6848   $95.68   $95.70   $95.70  
  Purchase #2 $194.34   7.847%   $209.5899   $209.59   $209.60   $209.60  
  Purchase #3 $10.70   3.770%   $11.1034   $11.10   $11.10   $11.10  
  Purchase #4 $118.57   3.828%   $123.1089   $123.11   $123.10   $123.10  
  Purchase #5 $130.98   7.789%   $141.182   $141.18   $141.20   $141.20  
  Purchase #6 $133.65   6.470%   $142.2972   $142.30   $142.30   $142.30  
  Purchase #7 $219.50   6.488%   $233.7412   $233.74   $233.75   $233.70  
  7 purchase totals = $896.09       $956.7074   $956.70   $956.75   $956.70