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	$11.42	7.442%	$12.2699	$12.27	$12.25	$12.30
Purchase #2	$172.57	12.370%	$193.9169	$193.92	$193.90	$193.90
Purchase #3	$35.52	6.523%	$37.837	$37.84	$37.85	$37.80
Purchase #4	$34.26	10.495%	$37.8556	$37.86	$37.85	$37.90
Purchase #5	$148.35	6.487%	$157.9735	$157.97	$157.95	$158.00
Purchase #6	$134.49	7.378%	$144.4127	$144.41	$144.40	$144.40
Purchase #7	$112.52	9.477%	$123.1835	$123.18	$123.20	$123.20
7 purchase totals =	$649.13		$707.4491	$707.45	$707.40	$707.50