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	$43.65	4.403%	$45.5719	$45.57	$45.55	$45.60
Purchase #2	$79.77	9.714%	$87.5189	$87.52	$87.50	$87.50
Purchase #3	$6.31	12.762%	$7.1153	$7.12	$7.10	$7.10
Purchase #4	$71.42	6.102%	$75.778	$75.78	$75.80	$75.80
Purchase #5	$88.86	13.198%	$100.5877	$100.59	$100.60	$100.60
Purchase #6	$199.84	10.807%	$221.4367	$221.44	$221.45	$221.40
Purchase #7	$131.60	3.345%	$136.002	$136.00	$136.00	$136.00
7 purchase totals =	$621.45		$674.0105	$674.02	$674.00	$674.00