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	$136.87	12.389%	$153.8268	$153.83	$153.85	$153.80
Purchase #2	$228.94	7.142%	$245.2909	$245.29	$245.30	$245.30
Purchase #3	$134.38	3.615%	$139.2378	$139.24	$139.25	$139.20
Purchase #4	$70.81	11.495%	$78.9496	$78.95	$78.95	$78.90
Purchase #5	$235.59	3.205%	$243.1407	$243.14	$243.15	$243.10
Purchase #6	$35.44	5.257%	$37.3031	$37.30	$37.30	$37.30
Purchase #7	$204.90	4.808%	$214.7516	$214.75	$214.75	$214.80
7 purchase totals =	$1,046.93		$1,112.5005	$1,112.50	$1,112.55	$1,112.40