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	$178.42	6.789%	$190.5329	$190.53	$190.55	$190.50
Purchase #2	$179.72	5.759%	$190.0701	$190.07	$190.05	$190.10
Purchase #3	$159.55	10.388%	$176.1241	$176.12	$176.10	$176.10
Purchase #4	$31.26	13.263%	$35.406	$35.41	$35.40	$35.40
Purchase #5	$190.47	13.229%	$215.6673	$215.67	$215.65	$215.70
Purchase #6	$18.91	7.249%	$20.2808	$20.28	$20.30	$20.30
Purchase #7	$225.48	13.594%	$256.1318	$256.13	$256.15	$256.10
7 purchase totals =	$983.81		$1,084.2130	$1,084.21	$1,084.20	$1,084.20