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	$180.41	7.769%	$194.4261	$194.43	$194.45	$194.40
Purchase #2	$129.60	13.131%	$146.6178	$146.62	$146.60	$146.60
Purchase #3	$81.31	10.170%	$89.5792	$89.58	$89.60	$89.60
Purchase #4	$140.77	5.742%	$148.853	$148.85	$148.85	$148.90
Purchase #5	$210.65	5.242%	$221.6923	$221.69	$221.70	$221.70
Purchase #6	$103.55	7.723%	$111.5472	$111.55	$111.55	$111.50
Purchase #7	$146.53	7.439%	$157.4304	$157.43	$157.45	$157.40
7 purchase totals =	$992.82		$1,070.1460	$1,070.15	$1,070.20	$1,070.10