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 $41.36   11.817%   $46.2475   $46.25   $46.25   $46.20  
  Purchase #2 $179.35   8.127%   $193.9258   $193.93   $193.95   $193.90  
  Purchase #3 $83.75   5.519%   $88.3722   $88.37   $88.35   $88.40  
  Purchase #4 $109.69   9.364%   $119.9614   $119.96   $119.95   $120.00  
  Purchase #5 $76.66   3.821%   $79.5892   $79.59   $79.60   $79.60  
  Purchase #6 $31.94   12.854%   $36.0456   $36.05   $36.05   $36.00  
  Purchase #7 $216.67   12.700%   $244.1871   $244.19   $244.20   $244.20  
  7 purchase totals = $739.42       $808.3288   $808.34   $808.35   $808.30