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	$83.86	10.218%	$92.4288	$92.43	$92.45	$92.40
Purchase #2	$104.81	13.402%	$118.8566	$118.86	$118.85	$118.90
Purchase #3	$235.80	3.129%	$243.1782	$243.18	$243.20	$243.20
Purchase #4	$161.67	13.746%	$183.8932	$183.89	$183.90	$183.90
Purchase #5	$116.51	11.653%	$130.0869	$130.09	$130.10	$130.10
Purchase #6	$144.52	4.640%	$151.2257	$151.23	$151.25	$151.20
Purchase #7	$132.54	3.113%	$136.666	$136.67	$136.65	$136.70
7 purchase totals =	$979.71		$1,056.3354	$1,056.35	$1,056.40	$1,056.40