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 $211.36   7.165%   $226.5039   $226.50   $226.50   $226.50  
  Purchase #2 $195.82   9.172%   $213.7806   $213.78   $213.80   $213.80  
  Purchase #3 $20.79   9.591%   $22.784   $22.78   $22.80   $22.80  
  Purchase #4 $193.36   5.863%   $204.6967   $204.70   $204.70   $204.70  
  Purchase #5 $117.59   13.306%   $133.2365   $133.24   $133.25   $133.20  
  Purchase #6 $131.75   10.300%   $145.3203   $145.32   $145.30   $145.30  
  Purchase #7 $82.47   4.221%   $85.9511   $85.95   $85.95   $86.00  
  7 purchase totals = $953.14       $1,032.2731   $1,032.27   $1,032.30   $1,032.30