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	$216.32	6.112%	$229.5415	$229.54	$229.55	$229.50
Purchase #2	$15.86	4.326%	$16.5461	$16.55	$16.55	$16.50
Purchase #3	$19.73	7.287%	$21.1677	$21.17	$21.15	$21.20
Purchase #4	$60.79	6.353%	$64.652	$64.65	$64.65	$64.70
Purchase #5	$72.86	6.352%	$77.4881	$77.49	$77.50	$77.50
Purchase #6	$48.65	10.668%	$53.84	$53.84	$53.85	$53.80
Purchase #7	$45.62	4.327%	$47.594	$47.59	$47.60	$47.60
7 purchase totals =	$479.83		$510.8294	$510.83	$510.85	$510.80