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 $207.39   4.650%   $217.0336   $217.03   $217.05   $217.00  
  Purchase #2 $151.88   11.323%   $169.0774   $169.08   $169.10   $169.10  
  Purchase #3 $36.74   11.727%   $41.0485   $41.05   $41.05   $41.00  
  Purchase #4 $115.38   3.375%   $119.2741   $119.27   $119.25   $119.30  
  Purchase #5 $167.53   10.386%   $184.9297   $184.93   $184.95   $184.90  
  Purchase #6 $234.74   11.311%   $261.2914   $261.29   $261.30   $261.30  
  Purchase #7 $165.43   4.449%   $172.79   $172.79   $172.80   $172.80  
  7 purchase totals = $1,079.09       $1,165.4447   $1,165.44   $1,165.50   $1,165.40