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 $167.68   6.252%   $178.1634   $178.16   $178.15   $178.20  
  Purchase #2 $224.43   8.772%   $244.117   $244.12   $244.10   $244.10  
  Purchase #3 $42.33   8.618%   $45.978   $45.98   $46.00   $46.00  
  Purchase #4 $248.34   8.537%   $269.5408   $269.54   $269.55   $269.50  
  Purchase #5 $182.83   6.331%   $194.405   $194.41   $194.40   $194.40  
  Purchase #6 $95.96   5.449%   $101.1889   $101.19   $101.20   $101.20  
  Purchase #7 $192.29   13.128%   $217.5338   $217.53   $217.55   $217.50  
  7 purchase totals = $1,153.86       $1,250.9269   $1,250.93   $1,250.95   $1,250.90