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	$172.73	11.647%	$192.8479	$192.85	$192.85	$192.80
Purchase #2	$81.96	13.337%	$92.891	$92.89	$92.90	$92.90
Purchase #3	$21.77	7.286%	$23.3562	$23.36	$23.35	$23.40
Purchase #4	$46.33	12.567%	$52.1523	$52.15	$52.15	$52.20
Purchase #5	$185.30	5.874%	$196.1845	$196.18	$196.20	$196.20
Purchase #6	$103.80	7.571%	$111.6587	$111.66	$111.65	$111.70
Purchase #7	$212.68	8.235%	$230.1942	$230.19	$230.20	$230.20
7 purchase totals =	$824.57		$899.2848	$899.28	$899.30	$899.40