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	$160.56	7.671%	$172.8766	$172.88	$172.90	$172.90
Purchase #2	$206.94	7.505%	$222.4708	$222.47	$222.45	$222.50
Purchase #3	$93.31	3.387%	$96.4704	$96.47	$96.45	$96.50
Purchase #4	$60.51	4.213%	$63.0593	$63.06	$63.05	$63.10
Purchase #5	$54.41	4.369%	$56.7872	$56.79	$56.80	$56.80
Purchase #6	$105.42	8.492%	$114.3723	$114.37	$114.35	$114.40
Purchase #7	$145.56	10.124%	$160.2965	$160.30	$160.30	$160.30
7 purchase totals =	$826.71		$886.3331	$886.34	$886.30	$886.50