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 $68.56   6.412%   $72.9561   $72.96   $72.95   $73.00  
  Purchase #2 $222.44   4.461%   $232.363   $232.36   $232.35   $232.40  
  Purchase #3 $22.39   4.616%   $23.4235   $23.42   $23.40   $23.40  
  Purchase #4 $197.38   6.449%   $210.109   $210.11   $210.10   $210.10  
  Purchase #5 $111.47   5.811%   $117.9475   $117.95   $117.95   $117.90  
  Purchase #6 $71.53   4.205%   $74.5378   $74.54   $74.55   $74.50  
  Purchase #7 $250.29   10.574%   $276.7557   $276.76   $276.75   $276.80  
  7 purchase totals = $944.06       $1,008.0926   $1,008.10   $1,008.05   $1,008.10