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	$107.64	3.620%	$111.5366	$111.54	$111.55	$111.50
Purchase #2	$48.95	8.485%	$53.1034	$53.10	$53.10	$53.10
Purchase #3	$16.94	12.793%	$19.1071	$19.11	$19.10	$19.10
Purchase #4	$34.51	6.548%	$36.7697	$36.77	$36.75	$36.80
Purchase #5	$172.69	7.443%	$185.5433	$185.54	$185.55	$185.50
Purchase #6	$37.98	6.170%	$40.3234	$40.32	$40.30	$40.30
Purchase #7	$41.33	4.606%	$43.2337	$43.23	$43.25	$43.20
7 purchase totals =	$460.04		$489.6172	$489.61	$489.60	$489.50