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	$156.66	7.855%	$168.9656	$168.97	$168.95	$169.00
Purchase #2	$90.42	10.339%	$99.7685	$99.77	$99.75	$99.80
Purchase #3	$213.80	12.362%	$240.23	$240.23	$240.25	$240.20
Purchase #4	$105.60	11.765%	$118.0238	$118.02	$118.00	$118.00
Purchase #5	$246.31	5.580%	$260.0541	$260.05	$260.05	$260.10
Purchase #6	$76.40	11.841%	$85.4465	$85.45	$85.45	$85.40
Purchase #7	$87.70	13.454%	$99.4992	$99.50	$99.50	$99.50
7 purchase totals =	$976.89		$1,071.9877	$1,071.99	$1,071.95	$1,072.00