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	$181.69	4.833%	$190.4711	$190.47	$190.45	$190.50
Purchase #2	$50.91	6.383%	$54.1596	$54.16	$54.15	$54.20
Purchase #3	$151.54	5.275%	$159.5337	$159.53	$159.55	$159.50
Purchase #4	$8.43	4.310%	$8.7933	$8.79	$8.80	$8.80
Purchase #5	$10.99	7.586%	$11.8237	$11.82	$11.80	$11.80
Purchase #6	$194.63	7.287%	$208.8127	$208.81	$208.80	$208.80
Purchase #7	$92.71	13.722%	$105.4317	$105.43	$105.45	$105.40
7 purchase totals =	$690.90		$739.0258	$739.01	$739.00	$739.00