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	$190.37	8.118%	$205.8242	$205.82	$205.80	$205.80
Purchase #2	$113.83	10.151%	$125.3849	$125.38	$125.40	$125.40
Purchase #3	$149.90	5.712%	$158.4623	$158.46	$158.45	$158.50
Purchase #4	$176.70	13.704%	$200.915	$200.92	$200.90	$200.90
Purchase #5	$210.87	3.609%	$218.4803	$218.48	$218.50	$218.50
Purchase #6	$180.90	10.775%	$200.392	$200.39	$200.40	$200.40
Purchase #7	$96.74	3.825%	$100.4403	$100.44	$100.45	$100.40
7 purchase totals =	$1,119.31		$1,209.8990	$1,209.89	$1,209.90	$1,209.90