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	$146.28	8.757%	$159.0897	$159.09	$159.10	$159.10
Purchase #2	$133.67	9.590%	$146.489	$146.49	$146.50	$146.50
Purchase #3	$54.83	7.508%	$58.9466	$58.95	$58.95	$58.90
Purchase #4	$210.61	8.332%	$228.158	$228.16	$228.15	$228.20
Purchase #5	$179.88	11.574%	$200.6993	$200.70	$200.70	$200.70
Purchase #6	$244.64	4.784%	$256.3436	$256.34	$256.35	$256.30
Purchase #7	$89.59	11.429%	$99.8292	$99.83	$99.85	$99.80
7 purchase totals =	$1,059.50		$1,149.5554	$1,149.56	$1,149.60	$1,149.50