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 $164.60   6.673%   $175.5838   $175.58   $175.60   $175.60  
  Purchase #2 $162.36   9.635%   $178.0034   $178.00   $178.00   $178.00  
  Purchase #3 $195.82   7.662%   $210.8237   $210.82   $210.80   $210.80  
  Purchase #4 $229.29   7.187%   $245.7691   $245.77   $245.75   $245.80  
  Purchase #5 $223.56   10.420%   $246.855   $246.86   $246.85   $246.90  
  Purchase #6 $52.46   10.775%   $58.1126   $58.11   $58.10   $58.10  
  Purchase #7 $233.32   9.707%   $255.9684   $255.97   $255.95   $256.00  
  7 purchase totals = $1,261.41       $1,371.1160   $1,371.11   $1,371.05   $1,371.20