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	$172.69	6.846%	$184.5124	$184.51	$184.50	$184.50
Purchase #2	$164.37	9.539%	$180.0493	$180.05	$180.05	$180.00
Purchase #3	$211.80	8.195%	$229.157	$229.16	$229.15	$229.20
Purchase #4	$45.75	10.348%	$50.4842	$50.48	$50.50	$50.50
Purchase #5	$32.38	7.839%	$34.9183	$34.92	$34.90	$34.90
Purchase #6	$160.86	8.110%	$173.9057	$173.91	$173.90	$173.90
Purchase #7	$250.49	3.229%	$258.5783	$258.58	$258.60	$258.60
7 purchase totals =	$1,038.34		$1,111.6052	$1,111.61	$1,111.60	$1,111.60