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 $68.95   4.660%   $72.1631   $72.16   $72.15   $72.20  
  Purchase #2 $230.42   10.445%   $254.4874   $254.49   $254.50   $254.50  
  Purchase #3 $149.81   12.648%   $168.758   $168.76   $168.75   $168.80  
  Purchase #4 $58.48   12.718%   $65.9175   $65.92   $65.90   $65.90  
  Purchase #5 $241.79   4.750%   $253.275   $253.28   $253.30   $253.30  
  Purchase #6 $217.36   12.349%   $244.2018   $244.20   $244.20   $244.20  
  Purchase #7 $217.29   5.249%   $228.6956   $228.70   $228.70   $228.70  
  7 purchase totals = $1,184.10       $1,287.4984   $1,287.51   $1,287.50   $1,287.60