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	$82.42	7.621%	$88.7012	$88.70	$88.70	$88.70
Purchase #2	$6.35	10.787%	$7.035	$7.04	$7.05	$7.00
Purchase #3	$108.43	7.160%	$116.1936	$116.19	$116.20	$116.20
Purchase #4	$149.92	6.380%	$159.4849	$159.48	$159.50	$159.50
Purchase #5	$49.89	7.238%	$53.501	$53.50	$53.50	$53.50
Purchase #6	$72.52	12.593%	$81.6524	$81.65	$81.65	$81.70
Purchase #7	$62.72	13.177%	$70.9846	$70.98	$71.00	$71.00
7 purchase totals =	$532.25		$577.5527	$577.54	$577.60	$577.60