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	$169.89	12.298%	$190.7831	$190.78	$190.80	$190.80
Purchase #2	$95.85	3.615%	$99.315	$99.32	$99.30	$99.30
Purchase #3	$24.92	4.860%	$26.1311	$26.13	$26.15	$26.10
Purchase #4	$94.43	13.865%	$107.5227	$107.52	$107.50	$107.50
Purchase #5	$172.61	11.107%	$191.7818	$191.78	$191.80	$191.80
Purchase #6	$182.81	4.260%	$190.5977	$190.60	$190.60	$190.60
Purchase #7	$49.36	8.308%	$53.4608	$53.46	$53.45	$53.50
7 purchase totals =	$789.87		$859.5922	$859.59	$859.60	$859.60