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 $33.41   5.702%   $35.315   $35.32   $35.30   $35.30  
  Purchase #2 $227.59   12.146%   $255.2331   $255.23   $255.25   $255.20  
  Purchase #3 $126.76   3.237%   $130.8632   $130.86   $130.85   $130.90  
  Purchase #4 $128.91   3.504%   $133.427   $133.43   $133.45   $133.40  
  Purchase #5 $187.98   3.253%   $194.095   $194.10   $194.10   $194.10  
  Purchase #6 $182.55   4.741%   $191.2047   $191.20   $191.20   $191.20  
  Purchase #7 $214.26   11.406%   $238.6985   $238.70   $238.70   $238.70  
  7 purchase totals = $1,101.46       $1,178.8365   $1,178.84   $1,178.85   $1,178.80