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	$239.56	6.192%	$254.3936	$254.39	$254.40	$254.40
Purchase #2	$131.45	3.841%	$136.499	$136.50	$136.50	$136.50
Purchase #3	$147.82	11.265%	$164.4719	$164.47	$164.45	$164.50
Purchase #4	$177.63	7.601%	$191.1317	$191.13	$191.15	$191.10
Purchase #5	$16.34	4.177%	$17.0225	$17.02	$17.00	$17.00
Purchase #6	$120.43	5.660%	$127.2463	$127.25	$127.25	$127.20
Purchase #7	$63.72	12.324%	$71.5729	$71.57	$71.55	$71.60
7 purchase totals =	$896.95		$962.3379	$962.33	$962.30	$962.30