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	$166.52	7.820%	$179.5419	$179.54	$179.55	$179.50
Purchase #2	$38.90	9.572%	$42.6235	$42.62	$42.60	$42.60
Purchase #3	$134.98	8.205%	$146.0551	$146.06	$146.05	$146.10
Purchase #4	$5.52	3.369%	$5.706	$5.71	$5.70	$5.70
Purchase #5	$230.79	7.220%	$247.453	$247.45	$247.45	$247.50
Purchase #6	$48.41	8.448%	$52.4997	$52.50	$52.50	$52.50
Purchase #7	$55.29	7.695%	$59.5446	$59.54	$59.55	$59.50
7 purchase totals =	$680.41		$733.4238	$733.42	$733.40	$733.40