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	$100.25	3.488%	$103.7467	$103.75	$103.75	$103.70
Purchase #2	$137.63	4.215%	$143.4311	$143.43	$143.45	$143.40
Purchase #3	$98.58	6.767%	$105.2509	$105.25	$105.25	$105.30
Purchase #4	$229.95	10.238%	$253.4923	$253.49	$253.50	$253.50
Purchase #5	$109.59	5.734%	$115.8739	$115.87	$115.85	$115.90
Purchase #6	$139.50	3.534%	$144.4299	$144.43	$144.45	$144.40
Purchase #7	$221.71	4.205%	$231.0329	$231.03	$231.05	$231.00
7 purchase totals =	$1,037.21		$1,097.2577	$1,097.25	$1,097.30	$1,097.20