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	$63.77	6.762%	$68.0821	$68.08	$68.10	$68.10
Purchase #2	$106.73	4.539%	$111.5745	$111.57	$111.55	$111.60
Purchase #3	$225.84	13.572%	$256.491	$256.49	$256.50	$256.50
Purchase #4	$237.63	9.572%	$260.3759	$260.38	$260.40	$260.40
Purchase #5	$133.70	13.495%	$151.7428	$151.74	$151.75	$151.70
Purchase #6	$43.59	11.182%	$48.4642	$48.46	$48.45	$48.50
Purchase #7	$87.69	13.605%	$99.6202	$99.62	$99.60	$99.60
7 purchase totals =	$898.95		$996.3507	$996.34	$996.35	$996.40