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	$173.51	13.210%	$196.4307	$196.43	$196.45	$196.40
Purchase #2	$181.90	9.718%	$199.577	$199.58	$199.60	$199.60
Purchase #3	$205.26	9.145%	$224.031	$224.03	$224.05	$224.00
Purchase #4	$165.92	5.639%	$175.2762	$175.28	$175.30	$175.30
Purchase #5	$35.42	4.850%	$37.1379	$37.14	$37.15	$37.10
Purchase #6	$189.71	11.822%	$212.1375	$212.14	$212.15	$212.10
Purchase #7	$236.52	3.846%	$245.6166	$245.62	$245.60	$245.60
7 purchase totals =	$1,188.24		$1,290.2069	$1,290.22	$1,290.30	$1,290.10