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 $66.47   11.774%   $74.2962   $74.30   $74.30   $74.30  
  Purchase #2 $231.52   3.428%   $239.4565   $239.46   $239.45   $239.50  
  Purchase #3 $240.26   12.368%   $269.9754   $269.98   $270.00   $270.00  
  Purchase #4 $244.94   3.518%   $253.557   $253.56   $253.55   $253.60  
  Purchase #5 $58.86   7.541%   $63.2986   $63.30   $63.30   $63.30  
  Purchase #6 $159.39   4.464%   $166.5052   $166.51   $166.50   $166.50  
  Purchase #7 $93.63   8.690%   $101.7664   $101.77   $101.75   $101.80  
  7 purchase totals = $1,095.07       $1,168.8553   $1,168.88   $1,168.85   $1,169.00