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	$139.84	5.479%	$147.5018	$147.50	$147.50	$147.50
Purchase #2	$201.35	7.735%	$216.9244	$216.92	$216.90	$216.90
Purchase #3	$176.94	6.762%	$188.9047	$188.90	$188.90	$188.90
Purchase #4	$64.71	12.635%	$72.8861	$72.89	$72.90	$72.90
Purchase #5	$122.93	4.519%	$128.4852	$128.49	$128.50	$128.50
Purchase #6	$145.74	8.714%	$158.4398	$158.44	$158.45	$158.40
Purchase #7	$222.71	3.414%	$230.3133	$230.31	$230.30	$230.30
7 purchase totals =	$1,074.22		$1,143.4553	$1,143.45	$1,143.45	$1,143.40