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	$43.50	3.635%	$45.0812	$45.08	$45.10	$45.10
Purchase #2	$146.38	10.789%	$162.1729	$162.17	$162.15	$162.20
Purchase #3	$55.78	11.411%	$62.1451	$62.15	$62.15	$62.10
Purchase #4	$45.91	3.553%	$47.5412	$47.54	$47.55	$47.50
Purchase #5	$162.79	6.798%	$173.8565	$173.86	$173.85	$173.90
Purchase #6	$222.78	9.852%	$244.7283	$244.73	$244.75	$244.70
Purchase #7	$70.38	12.476%	$79.1606	$79.16	$79.15	$79.20
7 purchase totals =	$747.52		$814.6858	$814.69	$814.70	$814.70