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	$190.70	10.145%	$210.0465	$210.05	$210.05	$210.00
Purchase #2	$20.37	9.175%	$22.2389	$22.24	$22.25	$22.20
Purchase #3	$17.48	12.489%	$19.6631	$19.66	$19.65	$19.70
Purchase #4	$49.56	9.758%	$54.3961	$54.40	$54.40	$54.40
Purchase #5	$32.84	13.511%	$37.277	$37.28	$37.30	$37.30
Purchase #6	$127.94	8.783%	$139.177	$139.18	$139.20	$139.20
Purchase #7	$82.65	9.782%	$90.7348	$90.73	$90.75	$90.70
7 purchase totals =	$521.54		$573.5334	$573.54	$573.60	$573.50