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	$52.48	7.864%	$56.607	$56.61	$56.60	$56.60
Purchase #2	$225.42	11.852%	$252.1368	$252.14	$252.15	$252.10
Purchase #3	$197.49	7.859%	$213.0107	$213.01	$213.00	$213.00
Purchase #4	$123.43	6.717%	$131.7208	$131.72	$131.70	$131.70
Purchase #5	$120.73	5.350%	$127.1891	$127.19	$127.20	$127.20
Purchase #6	$105.96	10.355%	$116.9322	$116.93	$116.95	$116.90
Purchase #7	$181.52	6.615%	$193.5275	$193.53	$193.55	$193.50
7 purchase totals =	$1,007.03		$1,091.1241	$1,091.13	$1,091.15	$1,091.00