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	$244.25	5.312%	$257.2246	$257.22	$257.20	$257.20
Purchase #2	$49.75	3.600%	$51.541	$51.54	$51.55	$51.50
Purchase #3	$243.71	10.323%	$268.8682	$268.87	$268.85	$268.90
Purchase #4	$224.91	6.847%	$240.3096	$240.31	$240.30	$240.30
Purchase #5	$111.45	7.273%	$119.5558	$119.56	$119.55	$119.60
Purchase #6	$130.89	5.657%	$138.2944	$138.29	$138.30	$138.30
Purchase #7	$162.89	10.250%	$179.5862	$179.59	$179.60	$179.60
7 purchase totals =	$1,167.85		$1,255.3798	$1,255.38	$1,255.35	$1,255.40