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	$128.27	12.242%	$143.9728	$143.97	$143.95	$144.00
Purchase #2	$106.50	11.621%	$118.8764	$118.88	$118.90	$118.90
Purchase #3	$205.34	13.605%	$233.2765	$233.28	$233.30	$233.30
Purchase #4	$115.75	12.752%	$130.5104	$130.51	$130.50	$130.50
Purchase #5	$10.84	6.264%	$11.519	$11.52	$11.50	$11.50
Purchase #6	$66.53	10.541%	$73.5429	$73.54	$73.55	$73.50
Purchase #7	$18.86	6.761%	$20.1351	$20.14	$20.15	$20.10
7 purchase totals =	$652.09		$731.8331	$731.84	$731.85	$731.80