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	$176.46	3.336%	$182.3467	$182.35	$182.35	$182.30
Purchase #2	$245.52	4.105%	$255.5986	$255.60	$255.60	$255.60
Purchase #3	$172.61	13.320%	$195.6017	$195.60	$195.60	$195.60
Purchase #4	$168.32	12.677%	$189.6579	$189.66	$189.65	$189.70
Purchase #5	$57.32	4.784%	$60.0622	$60.06	$60.05	$60.10
Purchase #6	$145.89	12.338%	$163.8899	$163.89	$163.90	$163.90
Purchase #7	$135.47	6.405%	$144.1469	$144.15	$144.15	$144.10
7 purchase totals =	$1,101.59		$1,191.3039	$1,191.31	$1,191.30	$1,191.30