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	$195.89	13.485%	$222.3058	$222.31	$222.30	$222.30
Purchase #2	$244.86	3.278%	$252.8865	$252.89	$252.90	$252.90
Purchase #3	$78.93	5.324%	$83.1322	$83.13	$83.15	$83.10
Purchase #4	$180.71	10.397%	$199.4984	$199.50	$199.50	$199.50
Purchase #5	$115.72	4.589%	$121.0304	$121.03	$121.05	$121.00
Purchase #6	$166.62	13.679%	$189.4119	$189.41	$189.40	$189.40
Purchase #7	$72.36	8.218%	$78.3065	$78.31	$78.30	$78.30
7 purchase totals =	$1,055.09		$1,146.5717	$1,146.58	$1,146.60	$1,146.50