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 $59.81   8.747%   $65.0416   $65.04   $65.05   $65.00  
  Purchase #2 $110.74   6.745%   $118.2094   $118.21   $118.20   $118.20  
  Purchase #3 $8.61   9.111%   $9.3945   $9.39   $9.40   $9.40  
  Purchase #4 $195.39   4.133%   $203.4655   $203.47   $203.45   $203.50  
  Purchase #5 $219.76   4.395%   $229.4185   $229.42   $229.40   $229.40  
  Purchase #6 $153.31   5.872%   $162.3124   $162.31   $162.30   $162.30  
  Purchase #7 $68.99   10.103%   $75.9601   $75.96   $75.95   $76.00  
  7 purchase totals = $816.61       $863.8020   $863.80   $863.75   $863.80