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	$106.49	4.650%	$111.4418	$111.44	$111.45	$111.40
Purchase #2	$81.62	12.117%	$91.5099	$91.51	$91.50	$91.50
Purchase #3	$247.50	11.728%	$276.5268	$276.53	$276.55	$276.50
Purchase #4	$181.57	9.630%	$199.0552	$199.06	$199.05	$199.10
Purchase #5	$112.28	6.652%	$119.7489	$119.75	$119.75	$119.70
Purchase #6	$119.76	6.716%	$127.8031	$127.80	$127.80	$127.80
Purchase #7	$9.78	13.253%	$11.0761	$11.08	$11.10	$11.10
7 purchase totals =	$859.00		$937.1618	$937.17	$937.20	$937.10