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	$31.95	4.523%	$33.3951	$33.40	$33.40	$33.40
Purchase #2	$204.38	5.116%	$214.8361	$214.84	$214.85	$214.80
Purchase #3	$133.93	13.158%	$151.5525	$151.55	$151.55	$151.60
Purchase #4	$47.96	13.183%	$54.2826	$54.28	$54.30	$54.30
Purchase #5	$170.29	5.339%	$179.3818	$179.38	$179.40	$179.40
Purchase #6	$87.74	3.113%	$90.4713	$90.47	$90.45	$90.50
Purchase #7	$242.91	4.766%	$254.4871	$254.49	$254.50	$254.50
7 purchase totals =	$919.16		$978.4065	$978.41	$978.45	$978.50