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 $208.81   11.123%   $232.0359   $232.04   $232.05   $232.00  
  Purchase #2 $223.42   4.585%   $233.6638   $233.66   $233.65   $233.70  
  Purchase #3 $86.53   10.163%   $95.324   $95.32   $95.30   $95.30  
  Purchase #4 $147.87   6.627%   $157.6693   $157.67   $157.65   $157.70  
  Purchase #5 $189.61   10.589%   $209.6878   $209.69   $209.70   $209.70  
  Purchase #6 $246.59   5.560%   $260.3004   $260.30   $260.30   $260.30  
  Purchase #7 $220.88   9.441%   $241.7333   $241.73   $241.75   $241.70  
  7 purchase totals = $1,323.71       $1,430.4145   $1,430.41   $1,430.40   $1,430.40