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	$205.62	11.688%	$229.6529	$229.65	$229.65	$229.70
Purchase #2	$112.52	6.180%	$119.4737	$119.47	$119.45	$119.50
Purchase #3	$55.84	11.280%	$62.1388	$62.14	$62.15	$62.10
Purchase #4	$41.37	10.263%	$45.6158	$45.62	$45.60	$45.60
Purchase #5	$174.47	3.555%	$180.6724	$180.67	$180.65	$180.70
Purchase #6	$222.97	4.840%	$233.7617	$233.76	$233.75	$233.80
Purchase #7	$55.75	10.858%	$61.8033	$61.80	$61.80	$61.80
7 purchase totals =	$868.54		$933.1186	$933.11	$933.05	$933.20