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 $205.25   9.483%   $224.7139   $224.71   $224.70   $224.70  
  Purchase #2 $203.67   5.534%   $214.9411   $214.94   $214.95   $214.90  
  Purchase #3 $82.42   3.779%   $85.5347   $85.53   $85.55   $85.50  
  Purchase #4 $131.69   9.304%   $143.9424   $143.94   $143.95   $143.90  
  Purchase #5 $157.51   6.612%   $167.9246   $167.92   $167.90   $167.90  
  Purchase #6 $136.50   9.342%   $149.2518   $149.25   $149.25   $149.30  
  Purchase #7 $175.74   6.420%   $187.0225   $187.02   $187.00   $187.00  
  7 purchase totals = $1,092.78       $1,173.3310   $1,173.31   $1,173.30   $1,173.20