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	$102.86	10.447%	$113.6058	$113.61	$113.60	$113.60
Purchase #2	$242.33	6.737%	$258.6558	$258.66	$258.65	$258.70
Purchase #3	$65.77	9.640%	$72.1102	$72.11	$72.10	$72.10
Purchase #4	$19.89	3.222%	$20.5309	$20.53	$20.55	$20.50
Purchase #5	$94.76	5.667%	$100.13	$100.13	$100.15	$100.10
Purchase #6	$65.70	12.228%	$73.7338	$73.73	$73.75	$73.70
Purchase #7	$129.73	11.763%	$144.9901	$144.99	$145.00	$145.00
7 purchase totals =	$721.04		$783.7566	$783.76	$783.80	$783.70