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 $114.57   4.413%   $119.626   $119.63   $119.65   $119.60  
  Purchase #2 $189.47   7.102%   $202.9262   $202.93   $202.95   $202.90  
  Purchase #3 $232.89   5.133%   $244.8442   $244.84   $244.85   $244.80  
  Purchase #4 $183.27   10.497%   $202.5079   $202.51   $202.50   $202.50  
  Purchase #5 $234.28   10.644%   $259.2168   $259.22   $259.20   $259.20  
  Purchase #6 $83.28   11.499%   $92.8564   $92.86   $92.85   $92.90  
  Purchase #7 $131.35   4.280%   $136.9718   $136.97   $136.95   $137.00  
  7 purchase totals = $1,169.11       $1,258.9493   $1,258.96   $1,258.95   $1,258.90