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	$144.60	11.439%	$161.1408	$161.14	$161.15	$161.10
Purchase #2	$239.80	9.832%	$263.3771	$263.38	$263.40	$263.40
Purchase #3	$221.88	11.709%	$247.8599	$247.86	$247.85	$247.90
Purchase #4	$192.39	12.676%	$216.7774	$216.78	$216.80	$216.80
Purchase #5	$245.92	4.464%	$256.8979	$256.90	$256.90	$256.90
Purchase #6	$128.94	9.407%	$141.0694	$141.07	$141.05	$141.10
Purchase #7	$111.37	10.686%	$123.271	$123.27	$123.25	$123.30
7 purchase totals =	$1,284.90		$1,410.3935	$1,410.40	$1,410.40	$1,410.50