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	$192.31	13.642%	$218.5449	$218.54	$218.55	$218.50
Purchase #2	$151.76	9.203%	$165.7265	$165.73	$165.75	$165.70
Purchase #3	$119.57	5.422%	$126.0531	$126.05	$126.05	$126.10
Purchase #4	$158.69	13.161%	$179.5752	$179.58	$179.60	$179.60
Purchase #5	$164.78	4.546%	$172.2709	$172.27	$172.25	$172.30
Purchase #6	$224.36	8.601%	$243.6572	$243.66	$243.65	$243.70
Purchase #7	$184.65	6.199%	$196.0965	$196.10	$196.10	$196.10
7 purchase totals =	$1,196.12		$1,301.9243	$1,301.93	$1,301.95	$1,302.00