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	$145.43	4.608%	$152.1314	$152.13	$152.15	$152.10
Purchase #2	$154.44	9.216%	$168.6732	$168.67	$168.65	$168.70
Purchase #3	$185.25	7.840%	$199.7736	$199.77	$199.75	$199.80
Purchase #4	$122.47	10.119%	$134.8627	$134.86	$134.85	$134.90
Purchase #5	$224.25	13.222%	$253.9003	$253.90	$253.90	$253.90
Purchase #6	$188.52	6.411%	$200.606	$200.61	$200.60	$200.60
Purchase #7	$5.60	8.654%	$6.0846	$6.08	$6.10	$6.10
7 purchase totals =	$1,025.96		$1,116.0318	$1,116.02	$1,116.00	$1,116.10