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	$113.31	3.690%	$117.4911	$117.49	$117.50	$117.50
Purchase #2	$70.45	4.825%	$73.8492	$73.85	$73.85	$73.80
Purchase #3	$39.94	13.757%	$45.4345	$45.43	$45.45	$45.40
Purchase #4	$186.78	6.820%	$199.5184	$199.52	$199.50	$199.50
Purchase #5	$134.28	13.613%	$152.5595	$152.56	$152.55	$152.60
Purchase #6	$123.58	7.726%	$133.1278	$133.13	$133.15	$133.10
Purchase #7	$250.80	10.635%	$277.4726	$277.47	$277.45	$277.50
7 purchase totals =	$919.14		$999.4531	$999.45	$999.45	$999.40