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	$231.98	5.320%	$244.3213	$244.32	$244.30	$244.30
Purchase #2	$221.72	5.130%	$233.0942	$233.09	$233.10	$233.10
Purchase #3	$179.59	11.201%	$199.7059	$199.71	$199.70	$199.70
Purchase #4	$91.71	7.510%	$98.5974	$98.60	$98.60	$98.60
Purchase #5	$156.49	12.858%	$176.6115	$176.61	$176.60	$176.60
Purchase #6	$40.30	3.645%	$41.7689	$41.77	$41.75	$41.80
Purchase #7	$94.68	6.443%	$100.7802	$100.78	$100.80	$100.80
7 purchase totals =	$1,016.47		$1,094.8794	$1,094.88	$1,094.85	$1,094.90