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	$187.77	12.495%	$211.2319	$211.23	$211.25	$211.20
Purchase #2	$54.81	9.230%	$59.869	$59.87	$59.85	$59.90
Purchase #3	$9.38	12.633%	$10.565	$10.57	$10.55	$10.60
Purchase #4	$81.87	5.681%	$86.521	$86.52	$86.50	$86.50
Purchase #5	$115.89	10.351%	$127.8858	$127.89	$127.90	$127.90
Purchase #6	$129.99	12.247%	$145.9099	$145.91	$145.90	$145.90
Purchase #7	$97.68	6.516%	$104.0448	$104.04	$104.05	$104.00
7 purchase totals =	$677.39		$746.0274	$746.03	$746.00	$746.00