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	$173.81	11.666%	$194.0867	$194.09	$194.10	$194.10
Purchase #2	$144.62	7.489%	$155.4506	$155.45	$155.45	$155.50
Purchase #3	$111.49	8.842%	$121.3479	$121.35	$121.35	$121.30
Purchase #4	$220.78	10.657%	$244.3085	$244.31	$244.30	$244.30
Purchase #5	$96.46	4.195%	$100.5065	$100.51	$100.50	$100.50
Purchase #6	$72.99	7.765%	$78.6577	$78.66	$78.65	$78.70
Purchase #7	$181.95	13.247%	$206.0529	$206.05	$206.05	$206.10
7 purchase totals =	$1,002.10		$1,100.4108	$1,100.42	$1,100.40	$1,100.50