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 $219.94   5.623%   $232.3072   $232.31   $232.30   $232.30  
  Purchase #2 $240.40   9.316%   $262.7957   $262.80   $262.80   $262.80  
  Purchase #3 $158.60   6.488%   $168.89   $168.89   $168.90   $168.90  
  Purchase #4 $152.67   10.874%   $169.2713   $169.27   $169.25   $169.30  
  Purchase #5 $164.63   5.197%   $173.1858   $173.19   $173.20   $173.20  
  Purchase #6 $101.52   4.769%   $106.3615   $106.36   $106.35   $106.40  
  Purchase #7 $218.51   6.753%   $233.266   $233.27   $233.25   $233.30  
  7 purchase totals = $1,256.27       $1,346.0775   $1,346.09   $1,346.05   $1,346.20