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 $142.67   5.163%   $150.0361   $150.04   $150.05   $150.00  
  Purchase #2 $203.39   5.317%   $214.2042   $214.20   $214.20   $214.20  
  Purchase #3 $125.66   5.721%   $132.849   $132.85   $132.85   $132.80  
  Purchase #4 $99.46   5.830%   $105.2585   $105.26   $105.25   $105.30  
  Purchase #5 $233.35   7.254%   $250.2772   $250.28   $250.30   $250.30  
  Purchase #6 $209.82   11.158%   $233.2317   $233.23   $233.25   $233.20  
  Purchase #7 $131.91   5.329%   $138.9395   $138.94   $138.95   $138.90  
  7 purchase totals = $1,146.26       $1,224.7962   $1,224.80   $1,224.85   $1,224.70