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	$209.75	13.821%	$238.7395	$238.74	$238.75	$238.70
Purchase #2	$126.74	5.562%	$133.7893	$133.79	$133.80	$133.80
Purchase #3	$50.76	9.440%	$55.5517	$55.55	$55.55	$55.60
Purchase #4	$241.76	11.243%	$268.9411	$268.94	$268.95	$268.90
Purchase #5	$108.60	4.605%	$113.601	$113.60	$113.60	$113.60
Purchase #6	$154.88	11.341%	$172.4449	$172.44	$172.45	$172.40
Purchase #7	$21.83	4.851%	$22.889	$22.89	$22.90	$22.90
7 purchase totals =	$914.32		$1,005.9565	$1,005.95	$1,006.00	$1,005.90