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	$160.42	7.425%	$172.3312	$172.33	$172.35	$172.30
Purchase #2	$83.64	9.773%	$91.8141	$91.81	$91.80	$91.80
Purchase #3	$131.29	4.800%	$137.5919	$137.59	$137.60	$137.60
Purchase #4	$87.56	5.291%	$92.1928	$92.19	$92.20	$92.20
Purchase #5	$82.41	3.229%	$85.071	$85.07	$85.05	$85.10
Purchase #6	$197.59	6.444%	$210.3227	$210.32	$210.30	$210.30
Purchase #7	$167.56	5.388%	$176.5881	$176.59	$176.60	$176.60
7 purchase totals =	$910.47		$965.9118	$965.90	$965.90	$965.90