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 $169.76   10.328%   $187.2928   $187.29   $187.30   $187.30  
  Purchase #2 $212.74   7.638%   $228.9891   $228.99   $229.00   $229.00  
  Purchase #3 $230.56   10.455%   $254.665   $254.67   $254.65   $254.70  
  Purchase #4 $223.40   13.603%   $253.7891   $253.79   $253.80   $253.80  
  Purchase #5 $242.41   12.306%   $272.241   $272.24   $272.25   $272.20  
  Purchase #6 $25.49   3.275%   $26.3248   $26.32   $26.30   $26.30  
  Purchase #7 $166.64   3.181%   $171.9408   $171.94   $171.95   $171.90  
  7 purchase totals = $1,271.00       $1,395.2426   $1,395.24   $1,395.25   $1,395.20