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	$188.29	13.825%	$214.3211	$214.32	$214.30	$214.30
Purchase #2	$58.72	11.447%	$65.4417	$65.44	$65.45	$65.40
Purchase #3	$228.48	5.227%	$240.4226	$240.42	$240.40	$240.40
Purchase #4	$19.79	10.442%	$21.8565	$21.86	$21.85	$21.90
Purchase #5	$37.94	12.231%	$42.5804	$42.58	$42.60	$42.60
Purchase #6	$229.62	10.301%	$253.2732	$253.27	$253.25	$253.30
Purchase #7	$152.42	4.363%	$159.0701	$159.07	$159.05	$159.10
7 purchase totals =	$915.26		$996.9656	$996.96	$996.90	$997.00