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	$206.32	8.423%	$223.6983	$223.70	$223.70	$223.70
Purchase #2	$230.72	10.130%	$254.0919	$254.09	$254.10	$254.10
Purchase #3	$73.49	6.356%	$78.161	$78.16	$78.15	$78.20
Purchase #4	$79.75	8.544%	$86.5638	$86.56	$86.55	$86.60
Purchase #5	$6.84	13.650%	$7.7737	$7.77	$7.75	$7.80
Purchase #6	$131.69	7.547%	$141.6286	$141.63	$141.65	$141.60
Purchase #7	$235.26	11.620%	$262.5972	$262.60	$262.60	$262.60
7 purchase totals =	$964.07		$1,054.5145	$1,054.51	$1,054.50	$1,054.60