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	$58.39	5.186%	$61.4181	$61.42	$61.40	$61.40
Purchase #2	$114.49	13.314%	$129.7332	$129.73	$129.75	$129.70
Purchase #3	$242.52	9.127%	$264.6548	$264.65	$264.65	$264.70
Purchase #4	$89.83	5.290%	$94.582	$94.58	$94.60	$94.60
Purchase #5	$145.89	9.792%	$160.1755	$160.18	$160.20	$160.20
Purchase #6	$84.40	13.406%	$95.7147	$95.71	$95.70	$95.70
Purchase #7	$247.75	11.128%	$275.3196	$275.32	$275.30	$275.30
7 purchase totals =	$983.27		$1,081.5979	$1,081.59	$1,081.60	$1,081.60