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 $167.36   4.168%   $174.3356   $174.34   $174.35   $174.30  
  Purchase #2 $34.74   3.652%   $36.0087   $36.01   $36.00   $36.00  
  Purchase #3 $42.82   8.431%   $46.4302   $46.43   $46.45   $46.40  
  Purchase #4 $165.34   11.593%   $184.5079   $184.51   $184.50   $184.50  
  Purchase #5 $246.75   10.361%   $272.3158   $272.32   $272.30   $272.30  
  Purchase #6 $111.41   11.474%   $124.1932   $124.19   $124.20   $124.20  
  Purchase #7 $113.56   4.419%   $118.5782   $118.58   $118.60   $118.60  
  7 purchase totals = $881.98       $956.3696   $956.38   $956.40   $956.30