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	$34.79	8.330%	$37.688	$37.69	$37.70	$37.70
Purchase #2	$159.71	10.785%	$176.9347	$176.93	$176.95	$176.90
Purchase #3	$95.65	9.810%	$105.0333	$105.03	$105.05	$105.00
Purchase #4	$185.82	13.461%	$210.8332	$210.83	$210.85	$210.80
Purchase #5	$117.72	12.395%	$132.3114	$132.31	$132.30	$132.30
Purchase #6	$240.85	6.434%	$256.3463	$256.35	$256.35	$256.30
Purchase #7	$236.82	5.831%	$250.629	$250.63	$250.65	$250.60
7 purchase totals =	$1,071.36		$1,169.7759	$1,169.77	$1,169.85	$1,169.60