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	$148.98	7.712%	$160.4693	$160.47	$160.45	$160.50
Purchase #2	$99.34	12.356%	$111.6145	$111.61	$111.60	$111.60
Purchase #3	$120.51	4.810%	$126.3065	$126.31	$126.30	$126.30
Purchase #4	$183.27	5.205%	$192.8092	$192.81	$192.80	$192.80
Purchase #5	$55.85	4.112%	$58.1466	$58.15	$58.15	$58.10
Purchase #6	$152.87	11.110%	$169.8539	$169.85	$169.85	$169.90
Purchase #7	$215.41	5.397%	$227.0357	$227.04	$227.05	$227.00
7 purchase totals =	$976.23		$1,046.2357	$1,046.24	$1,046.20	$1,046.20