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	$196.33	11.462%	$218.8333	$218.83	$218.85	$218.80
Purchase #2	$239.31	13.863%	$272.4855	$272.49	$272.50	$272.50
Purchase #3	$214.82	7.163%	$230.2076	$230.21	$230.20	$230.20
Purchase #4	$209.98	9.395%	$229.7076	$229.71	$229.70	$229.70
Purchase #5	$180.79	8.424%	$196.0197	$196.02	$196.00	$196.00
Purchase #6	$114.65	11.264%	$127.5642	$127.56	$127.55	$127.60
Purchase #7	$75.42	12.463%	$84.8196	$84.82	$84.80	$84.80
7 purchase totals =	$1,231.30		$1,359.6375	$1,359.64	$1,359.60	$1,359.60