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	$25.54	5.703%	$26.9965	$27.00	$27.00	$27.00
Purchase #2	$242.71	12.113%	$272.1095	$272.11	$272.10	$272.10
Purchase #3	$119.65	9.773%	$131.3434	$131.34	$131.35	$131.30
Purchase #4	$51.30	6.121%	$54.4401	$54.44	$54.45	$54.40
Purchase #5	$128.42	10.260%	$141.5959	$141.60	$141.60	$141.60
Purchase #6	$122.83	6.335%	$130.6113	$130.61	$130.60	$130.60
Purchase #7	$94.34	11.763%	$105.4372	$105.44	$105.45	$105.40
7 purchase totals =	$784.79		$862.5339	$862.54	$862.55	$862.40