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	$83.64	10.663%	$92.5585	$92.56	$92.55	$92.60
Purchase #2	$19.29	6.250%	$20.4956	$20.50	$20.50	$20.50
Purchase #3	$230.42	5.869%	$243.9433	$243.94	$243.95	$243.90
Purchase #4	$112.93	3.286%	$116.6409	$116.64	$116.65	$116.60
Purchase #5	$197.42	5.394%	$208.0688	$208.07	$208.05	$208.10
Purchase #6	$30.26	10.755%	$33.5145	$33.51	$33.50	$33.50
Purchase #7	$80.92	10.322%	$89.2726	$89.27	$89.25	$89.30
7 purchase totals =	$754.88		$804.4942	$804.49	$804.45	$804.50