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	$40.77	8.538%	$44.2509	$44.25	$44.25	$44.30
Purchase #2	$55.58	9.137%	$60.6583	$60.66	$60.65	$60.70
Purchase #3	$54.91	3.648%	$56.9131	$56.91	$56.90	$56.90
Purchase #4	$30.94	10.679%	$34.2441	$34.24	$34.25	$34.20
Purchase #5	$66.28	9.322%	$72.4586	$72.46	$72.45	$72.50
Purchase #6	$246.40	3.852%	$255.8913	$255.89	$255.90	$255.90
Purchase #7	$171.30	10.790%	$189.7833	$189.78	$189.80	$189.80
7 purchase totals =	$666.18		$714.1996	$714.19	$714.20	$714.30