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	$244.28	8.650%	$265.4102	$265.41	$265.40	$265.40
Purchase #2	$162.87	6.128%	$172.8507	$172.85	$172.85	$172.90
Purchase #3	$56.67	4.513%	$59.2275	$59.23	$59.25	$59.20
Purchase #4	$248.40	7.144%	$266.1457	$266.15	$266.15	$266.10
Purchase #5	$82.82	13.776%	$94.2293	$94.23	$94.25	$94.20
Purchase #6	$76.34	3.183%	$78.7699	$78.77	$78.75	$78.80
Purchase #7	$207.81	5.628%	$219.5055	$219.51	$219.50	$219.50
7 purchase totals =	$1,079.19		$1,156.1388	$1,156.15	$1,156.15	$1,156.10