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	$155.68	10.678%	$172.3035	$172.30	$172.30	$172.30
Purchase #2	$78.68	5.867%	$83.2962	$83.30	$83.30	$83.30
Purchase #3	$112.44	3.166%	$115.9999	$116.00	$116.00	$116.00
Purchase #4	$204.54	3.282%	$211.253	$211.25	$211.25	$211.30
Purchase #5	$92.69	11.307%	$103.1705	$103.17	$103.15	$103.20
Purchase #6	$109.81	11.302%	$122.2207	$122.22	$122.20	$122.20
Purchase #7	$89.38	12.816%	$100.8349	$100.83	$100.85	$100.80
7 purchase totals =	$843.22		$909.0787	$909.07	$909.05	$909.10