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	$232.87	10.264%	$256.7718	$256.77	$256.75	$256.80
Purchase #2	$196.27	10.827%	$217.5202	$217.52	$217.50	$217.50
Purchase #3	$70.47	11.113%	$78.3013	$78.30	$78.30	$78.30
Purchase #4	$232.58	11.701%	$259.7942	$259.79	$259.80	$259.80
Purchase #5	$51.65	12.799%	$58.2607	$58.26	$58.25	$58.30
Purchase #6	$22.33	11.203%	$24.8316	$24.83	$24.85	$24.80
Purchase #7	$157.38	9.675%	$172.6065	$172.61	$172.60	$172.60
7 purchase totals =	$963.55		$1,068.0863	$1,068.08	$1,068.05	$1,068.10