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	$78.52	3.250%	$81.0719	$81.07	$81.05	$81.10
Purchase #2	$159.61	10.251%	$175.9716	$175.97	$175.95	$176.00
Purchase #3	$245.71	4.567%	$256.9316	$256.93	$256.95	$256.90
Purchase #4	$198.65	3.815%	$206.2285	$206.23	$206.25	$206.20
Purchase #5	$87.50	4.613%	$91.5364	$91.54	$91.55	$91.50
Purchase #6	$132.60	5.119%	$139.3878	$139.39	$139.40	$139.40
Purchase #7	$160.98	3.483%	$166.5869	$166.59	$166.60	$166.60
7 purchase totals =	$1,063.57		$1,117.7147	$1,117.72	$1,117.75	$1,117.70