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	$99.93	3.738%	$103.6654	$103.67	$103.65	$103.70
Purchase #2	$154.29	12.864%	$174.1379	$174.14	$174.15	$174.10
Purchase #3	$239.89	6.496%	$255.4733	$255.47	$255.45	$255.50
Purchase #4	$120.53	9.609%	$132.1117	$132.11	$132.10	$132.10
Purchase #5	$29.62	12.547%	$33.3364	$33.34	$33.35	$33.30
Purchase #6	$104.78	10.380%	$115.6562	$115.66	$115.65	$115.70
Purchase #7	$188.49	4.384%	$196.7534	$196.75	$196.75	$196.80
7 purchase totals =	$937.53		$1,011.1343	$1,011.14	$1,011.10	$1,011.20