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	$167.96	7.187%	$180.0313	$180.03	$180.05	$180.00
Purchase #2	$121.35	10.665%	$134.292	$134.29	$134.30	$134.30
Purchase #3	$121.43	5.769%	$128.4353	$128.44	$128.45	$128.40
Purchase #4	$237.29	10.842%	$263.017	$263.02	$263.00	$263.00
Purchase #5	$96.89	9.555%	$106.1478	$106.15	$106.15	$106.10
Purchase #6	$148.29	5.543%	$156.5097	$156.51	$156.50	$156.50
Purchase #7	$76.30	5.622%	$80.5896	$80.59	$80.60	$80.60
7 purchase totals =	$969.51		$1,049.0227	$1,049.03	$1,049.05	$1,048.90