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	$117.54	8.145%	$127.1136	$127.11	$127.10	$127.10
Purchase #2	$122.44	6.836%	$130.81	$130.81	$130.80	$130.80
Purchase #3	$225.54	10.619%	$249.4901	$249.49	$249.50	$249.50
Purchase #4	$141.45	3.563%	$146.4899	$146.49	$146.50	$146.50
Purchase #5	$52.37	9.177%	$57.176	$57.18	$57.20	$57.20
Purchase #6	$171.32	8.643%	$186.1272	$186.13	$186.15	$186.10
Purchase #7	$104.29	6.496%	$111.0647	$111.06	$111.05	$111.10
7 purchase totals =	$934.95		$1,008.2715	$1,008.27	$1,008.30	$1,008.30