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 $176.94   3.121%   $182.4623   $182.46   $182.45   $182.50  
  Purchase #2 $189.75   3.608%   $196.5962   $196.60   $196.60   $196.60  
  Purchase #3 $210.36   10.516%   $232.4815   $232.48   $232.50   $232.50  
  Purchase #4 $216.97   3.485%   $224.5314   $224.53   $224.55   $224.50  
  Purchase #5 $131.89   11.405%   $146.9321   $146.93   $146.95   $146.90  
  Purchase #6 $155.85   5.803%   $164.894   $164.89   $164.90   $164.90  
  Purchase #7 $184.75   9.464%   $202.2347   $202.23   $202.25   $202.20  
  7 purchase totals = $1,266.51       $1,350.1322   $1,350.12   $1,350.20   $1,350.10