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	$106.59	8.389%	$115.5318	$115.53	$115.55	$115.50
Purchase #2	$89.71	11.710%	$100.215	$100.22	$100.20	$100.20
Purchase #3	$17.90	13.229%	$20.268	$20.27	$20.25	$20.30
Purchase #4	$233.77	4.376%	$243.9998	$244.00	$244.00	$244.00
Purchase #5	$34.79	8.391%	$37.7092	$37.71	$37.70	$37.70
Purchase #6	$205.25	3.237%	$211.8939	$211.89	$211.90	$211.90
Purchase #7	$130.42	11.849%	$145.8735	$145.87	$145.85	$145.90
7 purchase totals =	$818.43		$875.4912	$875.49	$875.45	$875.50