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	$196.55	3.769%	$203.958	$203.96	$203.95	$204.00
Purchase #2	$179.40	11.749%	$200.4777	$200.48	$200.50	$200.50
Purchase #3	$189.66	10.502%	$209.5781	$209.58	$209.60	$209.60
Purchase #4	$52.77	3.492%	$54.6127	$54.61	$54.60	$54.60
Purchase #5	$242.42	6.480%	$258.1288	$258.13	$258.15	$258.10
Purchase #6	$9.63	10.611%	$10.6518	$10.65	$10.65	$10.70
Purchase #7	$230.40	5.149%	$242.2633	$242.26	$242.25	$242.30
7 purchase totals =	$1,100.83		$1,179.6704	$1,179.67	$1,179.70	$1,179.80