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	$76.92	12.196%	$86.3012	$86.30	$86.30	$86.30
Purchase #2	$105.52	5.409%	$111.2276	$111.23	$111.25	$111.20
Purchase #3	$118.40	6.682%	$126.3115	$126.31	$126.30	$126.30
Purchase #4	$180.91	5.188%	$190.2956	$190.30	$190.30	$190.30
Purchase #5	$100.98	10.821%	$111.907	$111.91	$111.90	$111.90
Purchase #6	$33.51	13.858%	$38.1538	$38.15	$38.15	$38.20
Purchase #7	$175.30	4.222%	$182.7012	$182.70	$182.70	$182.70
7 purchase totals =	$791.54		$846.8979	$846.90	$846.90	$846.90