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 $13.95   4.733%   $14.6103   $14.61   $14.60   $14.60  
  Purchase #2 $215.50   10.377%   $237.8624   $237.86   $237.85   $237.90  
  Purchase #3 $28.63   3.431%   $29.6123   $29.61   $29.60   $29.60  
  Purchase #4 $216.62   9.653%   $237.5303   $237.53   $237.55   $237.50  
  Purchase #5 $98.74   6.150%   $104.8125   $104.81   $104.80   $104.80  
  Purchase #6 $96.89   9.356%   $105.955   $105.96   $105.95   $106.00  
  Purchase #7 $214.33   12.240%   $240.564   $240.56   $240.55   $240.60  
  7 purchase totals = $884.66       $970.9468   $970.94   $970.90   $971.00