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	$96.92	8.345%	$105.008	$105.01	$105.00	$105.00
Purchase #2	$222.67	10.397%	$245.821	$245.82	$245.80	$245.80
Purchase #3	$9.69	6.572%	$10.3268	$10.33	$10.35	$10.30
Purchase #4	$205.72	13.836%	$234.1834	$234.18	$234.20	$234.20
Purchase #5	$163.71	4.489%	$171.0589	$171.06	$171.05	$171.10
Purchase #6	$225.96	11.648%	$252.2798	$252.28	$252.30	$252.30
Purchase #7	$54.82	9.251%	$59.8914	$59.89	$59.90	$59.90
7 purchase totals =	$979.49		$1,078.5693	$1,078.57	$1,078.60	$1,078.60