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	$100.83	4.321%	$105.1869	$105.19	$105.20	$105.20
Purchase #2	$53.51	5.348%	$56.3717	$56.37	$56.35	$56.40
Purchase #3	$21.86	6.602%	$23.3032	$23.30	$23.30	$23.30
Purchase #4	$143.82	6.734%	$153.5048	$153.50	$153.50	$153.50
Purchase #5	$88.83	7.118%	$95.1529	$95.15	$95.15	$95.20
Purchase #6	$113.26	11.714%	$126.5273	$126.53	$126.55	$126.50
Purchase #7	$96.54	11.279%	$107.4287	$107.43	$107.45	$107.40
7 purchase totals =	$618.65		$667.4755	$667.47	$667.50	$667.50