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 $193.53   5.176%   $203.5471   $203.55   $203.55   $203.50  
  Purchase #2 $185.76   10.243%   $204.7874   $204.79   $204.80   $204.80  
  Purchase #3 $111.47   4.866%   $116.8941   $116.89   $116.90   $116.90  
  Purchase #4 $141.47   8.565%   $153.5869   $153.59   $153.60   $153.60  
  Purchase #5 $204.37   12.497%   $229.9101   $229.91   $229.90   $229.90  
  Purchase #6 $93.31   9.447%   $102.125   $102.13   $102.15   $102.10  
  Purchase #7 $58.46   11.442%   $65.149   $65.15   $65.15   $65.10  
  7 purchase totals = $988.37       $1,075.9996   $1,076.01   $1,076.05   $1,075.90