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	$112.86	3.814%	$117.1645	$117.16	$117.15	$117.20
Purchase #2	$118.96	6.775%	$127.0195	$127.02	$127.00	$127.00
Purchase #3	$123.45	10.211%	$136.0555	$136.06	$136.05	$136.10
Purchase #4	$195.72	8.162%	$211.6947	$211.69	$211.70	$211.70
Purchase #5	$139.93	5.872%	$148.1467	$148.15	$148.15	$148.10
Purchase #6	$99.55	11.686%	$111.1834	$111.18	$111.20	$111.20
Purchase #7	$105.25	5.259%	$110.7851	$110.79	$110.80	$110.80
7 purchase totals =	$895.72		$962.0494	$962.05	$962.05	$962.10