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	$102.55	8.383%	$111.1468	$111.15	$111.15	$111.10
Purchase #2	$129.27	11.320%	$143.9034	$143.90	$143.90	$143.90
Purchase #3	$166.31	10.776%	$184.2316	$184.23	$184.25	$184.20
Purchase #4	$60.36	3.449%	$62.4418	$62.44	$62.45	$62.40
Purchase #5	$113.86	11.474%	$126.9243	$126.92	$126.90	$126.90
Purchase #6	$102.32	8.847%	$111.3723	$111.37	$111.35	$111.40
Purchase #7	$21.92	4.754%	$22.9621	$22.96	$22.95	$23.00
7 purchase totals =	$696.59		$762.9823	$762.97	$762.95	$762.90