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	$231.46	10.539%	$255.8536	$255.85	$255.85	$255.90
Purchase #2	$175.59	3.117%	$181.0631	$181.06	$181.05	$181.10
Purchase #3	$125.96	10.463%	$139.1392	$139.14	$139.15	$139.10
Purchase #4	$19.50	5.238%	$20.5214	$20.52	$20.50	$20.50
Purchase #5	$145.43	6.459%	$154.8233	$154.82	$154.80	$154.80
Purchase #6	$100.71	8.686%	$109.4577	$109.46	$109.45	$109.50
Purchase #7	$33.63	4.448%	$35.1259	$35.13	$35.15	$35.10
7 purchase totals =	$832.28		$895.9842	$895.98	$895.95	$896.00