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	$228.61	7.161%	$244.9808	$244.98	$245.00	$245.00
Purchase #2	$38.33	13.640%	$43.5582	$43.56	$43.55	$43.60
Purchase #3	$153.25	3.670%	$158.8743	$158.87	$158.85	$158.90
Purchase #4	$73.49	7.226%	$78.8004	$78.80	$78.80	$78.80
Purchase #5	$138.44	7.509%	$148.8355	$148.84	$148.85	$148.80
Purchase #6	$165.79	10.222%	$182.7371	$182.74	$182.75	$182.70
Purchase #7	$64.94	8.469%	$70.4398	$70.44	$70.45	$70.40
7 purchase totals =	$862.85		$928.2261	$928.23	$928.25	$928.20