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	$57.77	3.131%	$59.5788	$59.58	$59.60	$59.60
Purchase #2	$246.74	12.523%	$277.6393	$277.64	$277.65	$277.60
Purchase #3	$205.49	5.651%	$217.1022	$217.10	$217.10	$217.10
Purchase #4	$71.39	7.852%	$76.9955	$77.00	$77.00	$77.00
Purchase #5	$199.89	10.623%	$221.1243	$221.12	$221.10	$221.10
Purchase #6	$79.82	9.670%	$87.5386	$87.54	$87.55	$87.50
Purchase #7	$103.83	6.477%	$110.5551	$110.56	$110.55	$110.60
7 purchase totals =	$964.93		$1,050.5338	$1,050.54	$1,050.55	$1,050.50