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	$52.59	9.535%	$57.6045	$57.60	$57.60	$57.60
Purchase #2	$74.81	11.230%	$83.2112	$83.21	$83.20	$83.20
Purchase #3	$233.68	9.531%	$255.952	$255.95	$255.95	$256.00
Purchase #4	$240.42	10.428%	$265.491	$265.49	$265.50	$265.50
Purchase #5	$66.86	8.337%	$72.4341	$72.43	$72.45	$72.40
Purchase #6	$65.68	7.292%	$70.4694	$70.47	$70.45	$70.50
Purchase #7	$222.27	8.164%	$240.4161	$240.42	$240.40	$240.40
7 purchase totals =	$956.31		$1,045.5783	$1,045.57	$1,045.55	$1,045.60