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	$135.40	11.396%	$150.8302	$150.83	$150.85	$150.80
Purchase #2	$96.70	9.359%	$105.7502	$105.75	$105.75	$105.80
Purchase #3	$10.69	13.662%	$12.1505	$12.15	$12.15	$12.20
Purchase #4	$108.68	8.836%	$118.283	$118.28	$118.30	$118.30
Purchase #5	$171.44	11.548%	$191.2379	$191.24	$191.25	$191.20
Purchase #6	$245.45	6.363%	$261.068	$261.07	$261.05	$261.10
Purchase #7	$165.92	3.824%	$172.2648	$172.26	$172.25	$172.30
7 purchase totals =	$934.28		$1,011.5846	$1,011.58	$1,011.60	$1,011.70