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 $44.35   4.287%   $46.2513   $46.25   $46.25   $46.30  
  Purchase #2 $209.96   11.615%   $234.3469   $234.35   $234.35   $234.30  
  Purchase #3 $161.35   4.471%   $168.564   $168.56   $168.55   $168.60  
  Purchase #4 $93.37   11.716%   $104.3092   $104.31   $104.30   $104.30  
  Purchase #5 $170.44   10.287%   $187.9732   $187.97   $187.95   $188.00  
  Purchase #6 $191.75   13.552%   $217.736   $217.74   $217.75   $217.70  
  Purchase #7 $184.74   8.112%   $199.7261   $199.73   $199.75   $199.70  
  7 purchase totals = $1,055.96       $1,158.9067   $1,158.91   $1,158.90   $1,158.90