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	$179.84	9.412%	$196.7665	$196.77	$196.75	$196.80
Purchase #2	$54.90	9.843%	$60.3038	$60.30	$60.30	$60.30
Purchase #3	$136.45	12.561%	$153.5895	$153.59	$153.60	$153.60
Purchase #4	$95.93	7.605%	$103.2255	$103.23	$103.25	$103.20
Purchase #5	$127.25	12.493%	$143.1473	$143.15	$143.15	$143.10
Purchase #6	$119.66	5.404%	$126.1264	$126.13	$126.15	$126.10
Purchase #7	$97.72	11.809%	$109.2598	$109.26	$109.25	$109.30
7 purchase totals =	$811.75		$892.4188	$892.43	$892.45	$892.40