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	$9.61	6.690%	$10.2529	$10.25	$10.25	$10.30
Purchase #2	$152.58	12.766%	$172.0584	$172.06	$172.05	$172.10
Purchase #3	$109.95	13.532%	$124.8284	$124.83	$124.85	$124.80
Purchase #4	$191.31	7.514%	$205.685	$205.69	$205.70	$205.70
Purchase #5	$99.97	4.472%	$104.4407	$104.44	$104.45	$104.40
Purchase #6	$191.27	7.145%	$204.9362	$204.94	$204.95	$204.90
Purchase #7	$199.77	12.212%	$224.1659	$224.17	$224.15	$224.20
7 purchase totals =	$954.46		$1,046.3675	$1,046.38	$1,046.40	$1,046.40