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	$148.86	6.216%	$158.1131	$158.11	$158.10	$158.10
Purchase #2	$167.67	3.604%	$173.7128	$173.71	$173.70	$173.70
Purchase #3	$50.81	6.492%	$54.1086	$54.11	$54.10	$54.10
Purchase #4	$41.63	12.287%	$46.7451	$46.75	$46.75	$46.70
Purchase #5	$95.48	5.142%	$100.3896	$100.39	$100.40	$100.40
Purchase #6	$111.81	12.694%	$126.0032	$126.00	$126.00	$126.00
Purchase #7	$93.56	6.727%	$99.8538	$99.85	$99.85	$99.90
7 purchase totals =	$709.82		$758.9262	$758.92	$758.90	$758.90