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	$50.47	3.195%	$52.0825	$52.08	$52.10	$52.10
Purchase #2	$229.30	12.467%	$257.8868	$257.89	$257.90	$257.90
Purchase #3	$139.95	5.455%	$147.5843	$147.58	$147.60	$147.60
Purchase #4	$168.28	11.327%	$187.3411	$187.34	$187.35	$187.30
Purchase #5	$210.85	11.687%	$235.492	$235.49	$235.50	$235.50
Purchase #6	$37.72	11.259%	$41.9669	$41.97	$41.95	$42.00
Purchase #7	$115.50	10.379%	$127.4877	$127.49	$127.50	$127.50
7 purchase totals =	$952.07		$1,049.8413	$1,049.84	$1,049.90	$1,049.90