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	$103.73	7.816%	$111.8375	$111.84	$111.85	$111.80
Purchase #2	$243.72	11.808%	$272.4985	$272.50	$272.50	$272.50
Purchase #3	$207.78	9.797%	$228.1362	$228.14	$228.15	$228.10
Purchase #4	$147.77	9.787%	$162.2322	$162.23	$162.25	$162.20
Purchase #5	$101.66	11.441%	$113.2909	$113.29	$113.30	$113.30
Purchase #6	$166.89	7.824%	$179.9475	$179.95	$179.95	$179.90
Purchase #7	$49.85	3.286%	$51.4881	$51.49	$51.50	$51.50
7 purchase totals =	$1,021.40		$1,119.4309	$1,119.44	$1,119.50	$1,119.30