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	$59.93	3.111%	$61.7944	$61.79	$61.80	$61.80
Purchase #2	$216.34	4.647%	$226.3933	$226.39	$226.40	$226.40
Purchase #3	$188.83	4.178%	$196.7193	$196.72	$196.70	$196.70
Purchase #4	$146.60	12.496%	$164.9191	$164.92	$164.90	$164.90
Purchase #5	$135.76	12.451%	$152.6635	$152.66	$152.65	$152.70
Purchase #6	$205.30	10.521%	$226.8996	$226.90	$226.90	$226.90
Purchase #7	$239.38	5.429%	$252.3759	$252.38	$252.40	$252.40
7 purchase totals =	$1,192.14		$1,281.7651	$1,281.76	$1,281.75	$1,281.80