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	$34.72	5.241%	$36.5397	$36.54	$36.55	$36.50
Purchase #2	$52.62	13.704%	$59.831	$59.83	$59.85	$59.80
Purchase #3	$118.37	10.798%	$131.1516	$131.15	$131.15	$131.20
Purchase #4	$162.60	10.563%	$179.7754	$179.78	$179.80	$179.80
Purchase #5	$58.68	10.331%	$64.7422	$64.74	$64.75	$64.70
Purchase #6	$214.43	13.778%	$243.9742	$243.97	$243.95	$244.00
Purchase #7	$141.33	3.160%	$145.796	$145.80	$145.80	$145.80
7 purchase totals =	$782.75		$861.8101	$861.81	$861.85	$861.80