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	$163.28	3.483%	$168.967	$168.97	$168.95	$169.00
Purchase #2	$172.94	8.769%	$188.1051	$188.11	$188.10	$188.10
Purchase #3	$220.84	11.256%	$245.6978	$245.70	$245.70	$245.70
Purchase #4	$192.95	10.186%	$212.6039	$212.60	$212.60	$212.60
Purchase #5	$18.82	6.700%	$20.0809	$20.08	$20.10	$20.10
Purchase #6	$199.68	4.872%	$209.4084	$209.41	$209.40	$209.40
Purchase #7	$89.26	12.608%	$100.5139	$100.51	$100.50	$100.50
7 purchase totals =	$1,057.77		$1,145.3770	$1,145.38	$1,145.35	$1,145.40