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	$216.25	4.160%	$225.246	$225.25	$225.25	$225.20
Purchase #2	$109.49	3.780%	$113.6287	$113.63	$113.65	$113.60
Purchase #3	$47.62	11.138%	$52.9239	$52.92	$52.90	$52.90
Purchase #4	$11.55	4.230%	$12.0386	$12.04	$12.05	$12.00
Purchase #5	$241.98	9.467%	$264.8882	$264.89	$264.90	$264.90
Purchase #6	$117.55	8.539%	$127.5876	$127.59	$127.60	$127.60
Purchase #7	$127.69	7.771%	$137.6128	$137.61	$137.60	$137.60
7 purchase totals =	$872.13		$933.9258	$933.93	$933.95	$933.80