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	$52.51	13.832%	$59.7732	$59.77	$59.75	$59.80
Purchase #2	$127.82	11.615%	$142.6663	$142.67	$142.65	$142.70
Purchase #3	$191.28	6.535%	$203.7801	$203.78	$203.80	$203.80
Purchase #4	$26.53	10.280%	$29.2573	$29.26	$29.25	$29.30
Purchase #5	$230.88	11.865%	$258.2739	$258.27	$258.25	$258.30
Purchase #6	$94.97	4.854%	$99.5798	$99.58	$99.60	$99.60
Purchase #7	$143.86	10.773%	$159.358	$159.36	$159.35	$159.40
7 purchase totals =	$867.85		$952.6886	$952.69	$952.65	$952.90