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 $94.45   7.726%   $101.7472   $101.75   $101.75   $101.70  
  Purchase #2 $145.90   4.258%   $152.1124   $152.11   $152.10   $152.10  
  Purchase #3 $125.44   5.660%   $132.5399   $132.54   $132.55   $132.50  
  Purchase #4 $72.67   7.200%   $77.9022   $77.90   $77.90   $77.90  
  Purchase #5 $187.47   9.322%   $204.946   $204.95   $204.95   $204.90  
  Purchase #6 $141.28   11.727%   $157.8479   $157.85   $157.85   $157.80  
  Purchase #7 $205.41   13.767%   $233.6888   $233.69   $233.70   $233.70  
  7 purchase totals = $972.62       $1,060.7844   $1,060.79   $1,060.80   $1,060.60