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	$133.27	9.274%	$145.6295	$145.63	$145.65	$145.60
Purchase #2	$203.63	9.322%	$222.6124	$222.61	$222.60	$222.60
Purchase #3	$71.93	7.845%	$77.5729	$77.57	$77.55	$77.60
Purchase #4	$152.60	7.797%	$164.4982	$164.50	$164.50	$164.50
Purchase #5	$188.89	9.578%	$206.9819	$206.98	$207.00	$207.00
Purchase #6	$100.86	4.162%	$105.0578	$105.06	$105.05	$105.10
Purchase #7	$82.65	4.250%	$86.1626	$86.16	$86.15	$86.20
7 purchase totals =	$933.83		$1,008.5153	$1,008.51	$1,008.50	$1,008.60