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	$114.52	11.191%	$127.3359	$127.34	$127.35	$127.30
Purchase #2	$202.95	7.260%	$217.6842	$217.68	$217.70	$217.70
Purchase #3	$179.80	5.406%	$189.52	$189.52	$189.50	$189.50
Purchase #4	$219.93	11.722%	$245.7102	$245.71	$245.70	$245.70
Purchase #5	$127.49	12.275%	$143.1394	$143.14	$143.15	$143.10
Purchase #6	$51.28	11.777%	$57.3192	$57.32	$57.30	$57.30
Purchase #7	$75.41	9.745%	$82.7587	$82.76	$82.75	$82.80
7 purchase totals =	$971.38		$1,063.4676	$1,063.47	$1,063.45	$1,063.40