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	$199.65	4.395%	$208.4246	$208.42	$208.40	$208.40
Purchase #2	$146.31	12.759%	$164.9777	$164.98	$165.00	$165.00
Purchase #3	$84.43	5.731%	$89.2687	$89.27	$89.25	$89.30
Purchase #4	$147.56	8.730%	$160.442	$160.44	$160.45	$160.40
Purchase #5	$40.53	11.781%	$45.3048	$45.30	$45.30	$45.30
Purchase #6	$188.52	6.247%	$200.2968	$200.30	$200.30	$200.30
Purchase #7	$240.75	10.608%	$266.2888	$266.29	$266.30	$266.30
7 purchase totals =	$1,047.75		$1,135.0034	$1,135.00	$1,135.00	$1,135.00