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 $172.38   13.127%   $195.0083   $195.01   $195.00   $195.00  
  Purchase #2 $130.51   9.418%   $142.8014   $142.80   $142.80   $142.80  
  Purchase #3 $69.68   11.674%   $77.8144   $77.81   $77.80   $77.80  
  Purchase #4 $249.45   7.531%   $268.2361   $268.24   $268.25   $268.20  
  Purchase #5 $141.97   9.326%   $155.2101   $155.21   $155.20   $155.20  
  Purchase #6 $183.62   8.461%   $199.1561   $199.16   $199.15   $199.20  
  Purchase #7 $228.41   12.392%   $256.7146   $256.71   $256.70   $256.70  
  7 purchase totals = $1,176.02       $1,294.9410   $1,294.94   $1,294.90   $1,294.90