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 $88.86   7.432%   $95.4641   $95.46   $95.45   $95.50  
  Purchase #2 $191.28   4.700%   $200.2702   $200.27   $200.25   $200.30  
  Purchase #3 $128.67   3.315%   $132.9354   $132.94   $132.95   $132.90  
  Purchase #4 $95.42   13.539%   $108.3389   $108.34   $108.35   $108.30  
  Purchase #5 $35.50   3.631%   $36.789   $36.79   $36.80   $36.80  
  Purchase #6 $234.84   11.829%   $262.6192   $262.62   $262.60   $262.60  
  Purchase #7 $244.86   13.442%   $277.7741   $277.77   $277.75   $277.80  
  7 purchase totals = $1,019.43       $1,114.1909   $1,114.19   $1,114.15   $1,114.20