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	$168.57	9.793%	$185.0781	$185.08	$185.10	$185.10
Purchase #2	$234.66	13.124%	$265.4568	$265.46	$265.45	$265.50
Purchase #3	$201.42	13.622%	$228.8574	$228.86	$228.85	$228.90
Purchase #4	$170.50	11.205%	$189.6045	$189.60	$189.60	$189.60
Purchase #5	$211.70	6.481%	$225.4203	$225.42	$225.40	$225.40
Purchase #6	$43.36	4.238%	$45.1976	$45.20	$45.20	$45.20
Purchase #7	$114.80	7.737%	$123.6821	$123.68	$123.70	$123.70
7 purchase totals =	$1,145.01		$1,263.2968	$1,263.30	$1,263.30	$1,263.40