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	$127.41	11.846%	$142.503	$142.50	$142.50	$142.50
Purchase #2	$174.50	12.745%	$196.74	$196.74	$196.75	$196.70
Purchase #3	$10.27	8.660%	$11.1594	$11.16	$11.15	$11.20
Purchase #4	$108.90	8.514%	$118.1717	$118.17	$118.15	$118.20
Purchase #5	$112.68	7.539%	$121.1749	$121.17	$121.15	$121.20
Purchase #6	$46.86	12.470%	$52.7034	$52.70	$52.70	$52.70
Purchase #7	$140.71	3.802%	$146.0598	$146.06	$146.05	$146.10
7 purchase totals =	$721.33		$788.5122	$788.50	$788.45	$788.60