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	$223.31	10.769%	$247.3583	$247.36	$247.35	$247.40
Purchase #2	$240.47	13.158%	$272.111	$272.11	$272.10	$272.10
Purchase #3	$161.55	6.729%	$172.4207	$172.42	$172.40	$172.40
Purchase #4	$37.86	9.562%	$41.4802	$41.48	$41.50	$41.50
Purchase #5	$63.88	8.261%	$69.1571	$69.16	$69.15	$69.20
Purchase #6	$84.42	7.373%	$90.6443	$90.64	$90.65	$90.60
Purchase #7	$120.82	6.846%	$129.0913	$129.09	$129.10	$129.10
7 purchase totals =	$932.31		$1,022.2629	$1,022.26	$1,022.25	$1,022.30