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	$67.89	9.727%	$74.4937	$74.49	$74.50	$74.50
Purchase #2	$172.89	9.212%	$188.8166	$188.82	$188.80	$188.80
Purchase #3	$85.62	4.600%	$89.5585	$89.56	$89.55	$89.60
Purchase #4	$109.99	3.489%	$113.8276	$113.83	$113.85	$113.80
Purchase #5	$39.85	13.346%	$45.1684	$45.17	$45.15	$45.20
Purchase #6	$210.59	10.534%	$232.7736	$232.77	$232.75	$232.80
Purchase #7	$10.78	5.532%	$11.3763	$11.38	$11.40	$11.40
7 purchase totals =	$697.61		$756.0147	$756.02	$756.00	$756.10