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 $146.35   4.507%   $152.946   $152.95   $152.95   $152.90  
  Purchase #2 $64.85   13.837%   $73.8233   $73.82   $73.80   $73.80  
  Purchase #3 $201.51   7.768%   $217.1633   $217.16   $217.15   $217.20  
  Purchase #4 $179.88   3.115%   $185.4833   $185.48   $185.50   $185.50  
  Purchase #5 $226.38   11.816%   $253.1291   $253.13   $253.15   $253.10  
  Purchase #6 $32.99   11.210%   $36.6882   $36.69   $36.70   $36.70  
  Purchase #7 $133.26   6.297%   $141.6514   $141.65   $141.65   $141.70  
  7 purchase totals = $985.22       $1,060.8846   $1,060.88   $1,060.90   $1,060.90