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 $33.29   8.366%   $36.075   $36.08   $36.10   $36.10  
  Purchase #2 $73.94   8.463%   $80.1975   $80.20   $80.20   $80.20  
  Purchase #3 $72.26   4.314%   $75.3773   $75.38   $75.40   $75.40  
  Purchase #4 $44.64   5.636%   $47.1559   $47.16   $47.15   $47.20  
  Purchase #5 $172.31   13.167%   $194.9981   $195.00   $195.00   $195.00  
  Purchase #6 $46.34   11.133%   $51.499   $51.50   $51.50   $51.50  
  Purchase #7 $210.27   7.734%   $226.5323   $226.53   $226.55   $226.50  
  7 purchase totals = $653.05       $711.8351   $711.85   $711.90   $711.90