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	$229.50	4.487%	$239.7977	$239.80	$239.80	$239.80
Purchase #2	$124.41	10.598%	$137.595	$137.60	$137.60	$137.60
Purchase #3	$43.49	4.313%	$45.3657	$45.37	$45.35	$45.40
Purchase #4	$221.64	9.318%	$242.2924	$242.29	$242.30	$242.30
Purchase #5	$93.54	3.681%	$96.9832	$96.98	$97.00	$97.00
Purchase #6	$243.40	6.370%	$258.9046	$258.90	$258.90	$258.90
Purchase #7	$129.51	13.110%	$146.4888	$146.49	$146.50	$146.50
7 purchase totals =	$1,085.49		$1,167.4274	$1,167.43	$1,167.45	$1,167.50