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	$177.28	8.492%	$192.3346	$192.33	$192.35	$192.30
Purchase #2	$170.63	13.215%	$193.1788	$193.18	$193.20	$193.20
Purchase #3	$47.30	13.861%	$53.8563	$53.86	$53.85	$53.90
Purchase #4	$181.65	4.485%	$189.797	$189.80	$189.80	$189.80
Purchase #5	$132.78	13.395%	$150.5659	$150.57	$150.55	$150.60
Purchase #6	$106.65	4.204%	$111.1336	$111.13	$111.15	$111.10
Purchase #7	$48.53	3.670%	$50.3111	$50.31	$50.30	$50.30
7 purchase totals =	$864.82		$941.1773	$941.18	$941.20	$941.20