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	$62.72	3.316%	$64.7998	$64.80	$64.80	$64.80
Purchase #2	$55.27	9.772%	$60.671	$60.67	$60.65	$60.70
Purchase #3	$189.38	13.388%	$214.7342	$214.73	$214.75	$214.70
Purchase #4	$130.88	11.572%	$146.0254	$146.03	$146.05	$146.00
Purchase #5	$65.51	11.167%	$72.8255	$72.83	$72.85	$72.80
Purchase #6	$148.89	12.556%	$167.5846	$167.58	$167.60	$167.60
Purchase #7	$40.94	5.371%	$43.1389	$43.14	$43.15	$43.10
7 purchase totals =	$693.59		$769.7794	$769.78	$769.85	$769.70