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 $44.31   3.214%   $45.7341   $45.73   $45.75   $45.70  
  Purchase #2 $244.57   8.769%   $266.0163   $266.02   $266.00   $266.00  
  Purchase #3 $64.94   6.510%   $69.1676   $69.17   $69.15   $69.20  
  Purchase #4 $150.38   12.507%   $169.188   $169.19   $169.20   $169.20  
  Purchase #5 $186.97   11.680%   $208.8081   $208.81   $208.80   $208.80  
  Purchase #6 $246.25   9.443%   $269.5034   $269.50   $269.50   $269.50  
  Purchase #7 $143.66   3.222%   $148.2887   $148.29   $148.30   $148.30  
  7 purchase totals = $1,081.08       $1,176.7062   $1,176.71   $1,176.70   $1,176.70