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	$98.34	5.333%	$103.5845	$103.58	$103.60	$103.60
Purchase #2	$112.76	13.125%	$127.5598	$127.56	$127.55	$127.60
Purchase #3	$165.91	4.206%	$172.8882	$172.89	$172.90	$172.90
Purchase #4	$229.78	3.362%	$237.5052	$237.51	$237.50	$237.50
Purchase #5	$88.44	6.789%	$94.4442	$94.44	$94.45	$94.40
Purchase #6	$214.60	6.833%	$229.2636	$229.26	$229.25	$229.30
Purchase #7	$17.26	11.630%	$19.2673	$19.27	$19.25	$19.30
7 purchase totals =	$927.09		$984.5128	$984.51	$984.50	$984.60