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	$85.38	10.719%	$94.5319	$94.53	$94.55	$94.50
Purchase #2	$60.68	9.225%	$66.2777	$66.28	$66.30	$66.30
Purchase #3	$17.32	7.430%	$18.6069	$18.61	$18.60	$18.60
Purchase #4	$97.48	3.330%	$100.7261	$100.73	$100.75	$100.70
Purchase #5	$148.86	12.379%	$167.2874	$167.29	$167.30	$167.30
Purchase #6	$17.76	13.326%	$20.1267	$20.13	$20.15	$20.10
Purchase #7	$170.29	13.394%	$193.0986	$193.10	$193.10	$193.10
7 purchase totals =	$597.77		$660.6553	$660.67	$660.75	$660.60