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	$37.95	13.400%	$43.0353	$43.04	$43.05	$43.00
Purchase #2	$48.44	12.135%	$54.3182	$54.32	$54.30	$54.30
Purchase #3	$155.71	6.344%	$165.5882	$165.59	$165.60	$165.60
Purchase #4	$50.35	13.577%	$57.186	$57.19	$57.20	$57.20
Purchase #5	$154.77	11.402%	$172.4169	$172.42	$172.40	$172.40
Purchase #6	$158.72	8.802%	$172.6905	$172.69	$172.70	$172.70
Purchase #7	$92.76	7.382%	$99.6075	$99.61	$99.60	$99.60
7 purchase totals =	$698.70		$764.8426	$764.86	$764.85	$764.80