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	$208.59	12.113%	$233.8565	$233.86	$233.85	$233.90
Purchase #2	$104.55	13.652%	$118.8232	$118.82	$118.80	$118.80
Purchase #3	$111.28	4.208%	$115.9627	$115.96	$115.95	$116.00
Purchase #4	$122.59	4.772%	$128.44	$128.44	$128.45	$128.40
Purchase #5	$204.50	9.305%	$223.5287	$223.53	$223.55	$223.50
Purchase #6	$126.76	3.551%	$131.2612	$131.26	$131.25	$131.30
Purchase #7	$225.88	9.742%	$247.8852	$247.89	$247.90	$247.90
7 purchase totals =	$1,104.15		$1,199.7575	$1,199.76	$1,199.75	$1,199.80