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	$65.28	10.312%	$72.0117	$72.01	$72.00	$72.00
Purchase #2	$223.82	3.798%	$232.3207	$232.32	$232.30	$232.30
Purchase #3	$43.65	4.635%	$45.6732	$45.67	$45.65	$45.70
Purchase #4	$144.97	3.520%	$150.0729	$150.07	$150.05	$150.10
Purchase #5	$67.78	8.593%	$73.6043	$73.60	$73.60	$73.60
Purchase #6	$80.67	13.807%	$91.8081	$91.81	$91.80	$91.80
Purchase #7	$55.86	10.439%	$61.6912	$61.69	$61.70	$61.70
7 purchase totals =	$682.03		$727.1821	$727.17	$727.10	$727.20