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	$226.32	11.241%	$251.7606	$251.76	$251.75	$251.80
Purchase #2	$183.83	3.695%	$190.6225	$190.62	$190.60	$190.60
Purchase #3	$50.71	6.782%	$54.1492	$54.15	$54.15	$54.10
Purchase #4	$39.77	11.686%	$44.4175	$44.42	$44.40	$44.40
Purchase #5	$97.87	13.554%	$111.1353	$111.14	$111.15	$111.10
Purchase #6	$48.88	3.123%	$50.4065	$50.41	$50.40	$50.40
Purchase #7	$220.30	11.566%	$245.7799	$245.78	$245.80	$245.80
7 purchase totals =	$867.68		$948.2715	$948.28	$948.25	$948.20