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	$63.53	4.307%	$66.2662	$66.27	$66.25	$66.30
Purchase #2	$176.45	5.323%	$185.8424	$185.84	$185.85	$185.80
Purchase #3	$233.75	4.513%	$244.2991	$244.30	$244.30	$244.30
Purchase #4	$78.95	10.705%	$87.4016	$87.40	$87.40	$87.40
Purchase #5	$37.31	13.244%	$42.2513	$42.25	$42.25	$42.30
Purchase #6	$111.85	4.280%	$116.6372	$116.64	$116.65	$116.60
Purchase #7	$201.71	4.343%	$210.4703	$210.47	$210.45	$210.50
7 purchase totals =	$903.55		$953.1681	$953.17	$953.15	$953.20