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 $85.42   12.436%   $96.0428   $96.04   $96.05   $96.00  
  Purchase #2 $140.49   10.863%   $155.7514   $155.75   $155.75   $155.80  
  Purchase #3 $204.54   12.831%   $230.7845   $230.78   $230.80   $230.80  
  Purchase #4 $112.46   5.855%   $119.0445   $119.04   $119.05   $119.00  
  Purchase #5 $109.82   8.606%   $119.2711   $119.27   $119.25   $119.30  
  Purchase #6 $59.38   8.471%   $64.4101   $64.41   $64.40   $64.40  
  Purchase #7 $150.54   11.620%   $168.0327   $168.03   $168.05   $168.00  
  7 purchase totals = $862.65       $953.3371   $953.32   $953.35   $953.30