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	$159.41	13.646%	$181.1631	$181.16	$181.15	$181.20
Purchase #2	$20.78	6.718%	$22.176	$22.18	$22.20	$22.20
Purchase #3	$219.93	10.698%	$243.4581	$243.46	$243.45	$243.50
Purchase #4	$78.58	4.506%	$82.1208	$82.12	$82.10	$82.10
Purchase #5	$11.78	3.478%	$12.1897	$12.19	$12.20	$12.20
Purchase #6	$161.51	6.771%	$172.4458	$172.45	$172.45	$172.40
Purchase #7	$9.66	6.805%	$10.3174	$10.32	$10.30	$10.30
7 purchase totals =	$661.65		$723.8709	$723.88	$723.85	$723.90