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 $189.76   3.185%   $195.8039   $195.80   $195.80   $195.80  
  Purchase #2 $250.98   10.358%   $276.9765   $276.98   $277.00   $277.00  
  Purchase #3 $31.67   10.714%   $35.0631   $35.06   $35.05   $35.10  
  Purchase #4 $200.28   8.237%   $216.7771   $216.78   $216.80   $216.80  
  Purchase #5 $35.64   5.709%   $37.6747   $37.67   $37.65   $37.70  
  Purchase #6 $154.79   5.262%   $162.935   $162.94   $162.95   $162.90  
  Purchase #7 $191.99   5.840%   $203.2022   $203.20   $203.20   $203.20  
  7 purchase totals = $1,055.11       $1,128.4325   $1,128.43   $1,128.45   $1,128.50