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	$211.98	9.640%	$232.4149	$232.41	$232.40	$232.40
Purchase #2	$14.27	6.253%	$15.1623	$15.16	$15.15	$15.20
Purchase #3	$90.65	10.769%	$100.4121	$100.41	$100.40	$100.40
Purchase #4	$150.72	3.297%	$155.6892	$155.69	$155.70	$155.70
Purchase #5	$241.66	6.240%	$256.7396	$256.74	$256.75	$256.70
Purchase #6	$160.46	11.245%	$178.5037	$178.50	$178.50	$178.50
Purchase #7	$123.78	12.207%	$138.8898	$138.89	$138.90	$138.90
7 purchase totals =	$993.52		$1,077.8116	$1,077.80	$1,077.80	$1,077.80