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	$144.69	4.392%	$151.0448	$151.04	$151.05	$151.00
Purchase #2	$198.99	11.838%	$222.5464	$222.55	$222.55	$222.50
Purchase #3	$241.87	13.800%	$275.2481	$275.25	$275.25	$275.20
Purchase #4	$191.32	8.826%	$208.2059	$208.21	$208.20	$208.20
Purchase #5	$205.91	5.805%	$217.8631	$217.86	$217.85	$217.90
Purchase #6	$97.55	6.156%	$103.5552	$103.56	$103.55	$103.60
Purchase #7	$140.55	7.633%	$151.2782	$151.28	$151.30	$151.30
7 purchase totals =	$1,220.88		$1,329.7417	$1,329.75	$1,329.75	$1,329.70