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	$151.71	6.103%	$160.9689	$160.97	$160.95	$161.00
Purchase #2	$74.35	12.346%	$83.5293	$83.53	$83.55	$83.50
Purchase #3	$227.26	8.661%	$246.943	$246.94	$246.95	$246.90
Purchase #4	$103.80	5.191%	$109.1883	$109.19	$109.20	$109.20
Purchase #5	$77.86	11.168%	$86.5554	$86.56	$86.55	$86.60
Purchase #6	$232.26	4.844%	$243.5107	$243.51	$243.50	$243.50
Purchase #7	$51.89	7.703%	$55.8871	$55.89	$55.90	$55.90
7 purchase totals =	$919.13		$986.5827	$986.59	$986.60	$986.60