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	$134.61	5.533%	$142.058	$142.06	$142.05	$142.10
Purchase #2	$102.26	8.687%	$111.1433	$111.14	$111.15	$111.10
Purchase #3	$137.29	7.533%	$147.6321	$147.63	$147.65	$147.60
Purchase #4	$171.62	9.279%	$187.5446	$187.54	$187.55	$187.50
Purchase #5	$82.56	12.438%	$92.8288	$92.83	$92.85	$92.80
Purchase #6	$122.62	6.762%	$130.9116	$130.91	$130.90	$130.90
Purchase #7	$66.92	5.308%	$70.4721	$70.47	$70.45	$70.50
7 purchase totals =	$817.88		$882.5905	$882.58	$882.60	$882.50