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	$190.31	4.278%	$198.4515	$198.45	$198.45	$198.50
Purchase #2	$229.55	9.688%	$251.7888	$251.79	$251.80	$251.80
Purchase #3	$133.27	4.836%	$139.7149	$139.71	$139.70	$139.70
Purchase #4	$16.67	10.767%	$18.4649	$18.46	$18.45	$18.50
Purchase #5	$130.74	10.631%	$144.639	$144.64	$144.65	$144.60
Purchase #6	$222.93	7.146%	$238.8606	$238.86	$238.85	$238.90
Purchase #7	$113.72	11.727%	$127.0559	$127.06	$127.05	$127.10
7 purchase totals =	$1,037.19		$1,118.9756	$1,118.97	$1,118.95	$1,119.10