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	$37.65	9.317%	$41.1579	$41.16	$41.15	$41.20
Purchase #2	$68.69	3.687%	$71.2226	$71.22	$71.20	$71.20
Purchase #3	$56.25	6.555%	$59.9372	$59.94	$59.95	$59.90
Purchase #4	$137.81	4.249%	$143.6655	$143.67	$143.65	$143.70
Purchase #5	$91.49	8.573%	$99.3334	$99.33	$99.35	$99.30
Purchase #6	$167.66	10.156%	$184.6875	$184.69	$184.70	$184.70
Purchase #7	$139.61	12.115%	$156.5238	$156.52	$156.50	$156.50
7 purchase totals =	$699.16		$756.5279	$756.53	$756.50	$756.50