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	$129.67	10.607%	$143.4241	$143.42	$143.40	$143.40
Purchase #2	$204.59	11.315%	$227.7394	$227.74	$227.75	$227.70
Purchase #3	$39.68	8.615%	$43.0984	$43.10	$43.10	$43.10
Purchase #4	$37.86	13.418%	$42.9401	$42.94	$42.95	$42.90
Purchase #5	$61.68	7.847%	$66.52	$66.52	$66.50	$66.50
Purchase #6	$173.74	12.215%	$194.9623	$194.96	$194.95	$195.00
Purchase #7	$225.39	8.182%	$243.8314	$243.83	$243.85	$243.80
7 purchase totals =	$872.61		$962.5157	$962.51	$962.50	$962.40