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 $92.46   5.356%   $97.4122   $97.41   $97.40   $97.40  
  Purchase #2 $245.34   11.533%   $273.6351   $273.64   $273.65   $273.60  
  Purchase #3 $163.41   9.726%   $179.3033   $179.30   $179.30   $179.30  
  Purchase #4 $194.40   8.808%   $211.5228   $211.52   $211.50   $211.50  
  Purchase #5 $28.89   12.205%   $32.416   $32.42   $32.40   $32.40  
  Purchase #6 $97.49   6.873%   $104.1905   $104.19   $104.20   $104.20  
  Purchase #7 $230.68   9.748%   $253.1667   $253.17   $253.15   $253.20  
  7 purchase totals = $1,052.67       $1,151.6466   $1,151.65   $1,151.60   $1,151.60