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 $244.60   4.496%   $255.5972   $255.60   $255.60   $255.60  
  Purchase #2 $44.66   5.635%   $47.1766   $47.18   $47.20   $47.20  
  Purchase #3 $121.71   4.820%   $127.5764   $127.58   $127.60   $127.60  
  Purchase #4 $209.83   6.306%   $223.0619   $223.06   $223.05   $223.10  
  Purchase #5 $206.93   9.197%   $225.9614   $225.96   $225.95   $226.00  
  Purchase #6 $217.54   10.422%   $240.212   $240.21   $240.20   $240.20  
  Purchase #7 $212.89   5.842%   $225.327   $225.33   $225.35   $225.30  
  7 purchase totals = $1,258.16       $1,344.9125   $1,344.92   $1,344.95   $1,345.00