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 $193.50   11.631%   $216.006   $216.01   $216.00   $216.00  
  Purchase #2 $207.78   11.525%   $231.7266   $231.73   $231.75   $231.70  
  Purchase #3 $53.37   7.237%   $57.2324   $57.23   $57.25   $57.20  
  Purchase #4 $215.78   8.438%   $233.9875   $233.99   $234.00   $234.00  
  Purchase #5 $156.59   10.455%   $172.9615   $172.96   $172.95   $173.00  
  Purchase #6 $74.70   6.177%   $79.3142   $79.31   $79.30   $79.30  
  Purchase #7 $169.33   6.671%   $180.626   $180.63   $180.65   $180.60  
  7 purchase totals = $1,071.05       $1,171.8542   $1,171.86   $1,171.90   $1,171.80