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 $118.75   5.566%   $125.3596   $125.36   $125.35   $125.40  
  Purchase #2 $54.42   11.817%   $60.8508   $60.85   $60.85   $60.90  
  Purchase #3 $133.79   9.450%   $146.4332   $146.43   $146.45   $146.40  
  Purchase #4 $188.85   3.625%   $195.6958   $195.70   $195.70   $195.70  
  Purchase #5 $178.38   12.783%   $201.1823   $201.18   $201.20   $201.20  
  Purchase #6 $202.44   12.862%   $228.4778   $228.48   $228.50   $228.50  
  Purchase #7 $140.27   5.582%   $148.0999   $148.10   $148.10   $148.10  
  7 purchase totals = $1,016.90       $1,106.0994   $1,106.10   $1,106.15   $1,106.20