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	$156.84	6.732%	$167.3985	$167.40	$167.40	$167.40
Purchase #2	$136.37	11.592%	$152.178	$152.18	$152.20	$152.20
Purchase #3	$192.83	12.659%	$217.2403	$217.24	$217.25	$217.20
Purchase #4	$170.96	13.689%	$194.3627	$194.36	$194.35	$194.40
Purchase #5	$100.95	10.332%	$111.3802	$111.38	$111.40	$111.40
Purchase #6	$174.73	5.462%	$184.2738	$184.27	$184.25	$184.30
Purchase #7	$76.58	3.835%	$79.5168	$79.52	$79.50	$79.50
7 purchase totals =	$1,009.26		$1,106.3503	$1,106.35	$1,106.35	$1,106.40