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	$99.31	13.448%	$112.6652	$112.67	$112.65	$112.70
Purchase #2	$18.91	10.698%	$20.933	$20.93	$20.95	$20.90
Purchase #3	$250.50	3.356%	$258.9068	$258.91	$258.90	$258.90
Purchase #4	$176.94	11.225%	$196.8015	$196.80	$196.80	$196.80
Purchase #5	$156.62	5.552%	$165.3155	$165.32	$165.30	$165.30
Purchase #6	$172.41	11.455%	$192.1596	$192.16	$192.15	$192.20
Purchase #7	$10.96	11.457%	$12.2157	$12.22	$12.20	$12.20
7 purchase totals =	$885.65		$958.9973	$959.01	$958.95	$959.00