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	$241.80	5.119%	$254.1777	$254.18	$254.20	$254.20
Purchase #2	$91.40	9.574%	$100.1506	$100.15	$100.15	$100.20
Purchase #3	$48.33	4.439%	$50.4754	$50.48	$50.50	$50.50
Purchase #4	$42.51	8.526%	$46.1344	$46.13	$46.15	$46.10
Purchase #5	$74.67	10.180%	$82.2714	$82.27	$82.25	$82.30
Purchase #6	$84.61	3.411%	$87.496	$87.50	$87.50	$87.50
Purchase #7	$163.76	5.285%	$172.4147	$172.41	$172.40	$172.40
7 purchase totals =	$747.08		$793.1202	$793.12	$793.15	$793.20