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	$169.64	13.629%	$192.7602	$192.76	$192.75	$192.80
Purchase #2	$54.75	4.174%	$57.0353	$57.04	$57.05	$57.00
Purchase #3	$53.91	4.568%	$56.3726	$56.37	$56.35	$56.40
Purchase #4	$210.93	5.423%	$222.3687	$222.37	$222.35	$222.40
Purchase #5	$239.50	7.250%	$256.8638	$256.86	$256.85	$256.90
Purchase #6	$31.31	7.349%	$33.611	$33.61	$33.60	$33.60
Purchase #7	$58.68	13.759%	$66.7538	$66.75	$66.75	$66.80
7 purchase totals =	$818.72		$885.7654	$885.76	$885.70	$885.90