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	$62.54	11.753%	$69.8903	$69.89	$69.90	$69.90
Purchase #2	$91.42	13.191%	$103.4792	$103.48	$103.50	$103.50
Purchase #3	$210.57	10.420%	$232.5114	$232.51	$232.50	$232.50
Purchase #4	$145.66	13.499%	$165.3226	$165.32	$165.30	$165.30
Purchase #5	$107.37	4.300%	$111.9869	$111.99	$112.00	$112.00
Purchase #6	$207.93	4.167%	$216.5944	$216.59	$216.60	$216.60
Purchase #7	$189.69	4.317%	$197.8789	$197.88	$197.90	$197.90
7 purchase totals =	$1,015.18		$1,097.6637	$1,097.66	$1,097.70	$1,097.70