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 $210.96   7.250%   $226.2546   $226.25   $226.25   $226.30  
  Purchase #2 $231.71   9.543%   $253.8221   $253.82   $253.80   $253.80  
  Purchase #3 $49.34   4.648%   $51.6333   $51.63   $51.65   $51.60  
  Purchase #4 $104.73   4.826%   $109.7843   $109.78   $109.80   $109.80  
  Purchase #5 $177.74   10.811%   $196.9555   $196.96   $196.95   $197.00  
  Purchase #6 $35.26   3.544%   $36.5096   $36.51   $36.50   $36.50  
  Purchase #7 $193.53   10.520%   $213.8894   $213.89   $213.90   $213.90  
  7 purchase totals = $1,003.27       $1,088.8488   $1,088.84   $1,088.85   $1,088.90