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	$9.40	6.537%	$10.0145	$10.01	$10.00	$10.00
Purchase #2	$147.89	13.584%	$167.9794	$167.98	$168.00	$168.00
Purchase #3	$93.51	7.726%	$100.7346	$100.73	$100.75	$100.70
Purchase #4	$52.42	3.564%	$54.2882	$54.29	$54.30	$54.30
Purchase #5	$187.47	4.613%	$196.118	$196.12	$196.10	$196.10
Purchase #6	$141.28	4.635%	$147.8283	$147.83	$147.85	$147.80
Purchase #7	$185.43	7.798%	$199.8898	$199.89	$199.90	$199.90
7 purchase totals =	$817.40		$876.8528	$876.85	$876.90	$876.80