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	$134.62	10.742%	$149.0809	$149.08	$149.10	$149.10
Purchase #2	$89.53	7.537%	$96.2779	$96.28	$96.30	$96.30
Purchase #3	$33.62	11.591%	$37.5169	$37.52	$37.50	$37.50
Purchase #4	$45.66	10.177%	$50.3068	$50.31	$50.30	$50.30
Purchase #5	$56.35	10.305%	$62.1569	$62.16	$62.15	$62.20
Purchase #6	$27.74	6.725%	$29.6055	$29.61	$29.60	$29.60
Purchase #7	$16.52	9.568%	$18.1006	$18.10	$18.10	$18.10
7 purchase totals =	$404.04		$443.0455	$443.06	$443.05	$443.10