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	$217.57	7.556%	$234.0096	$234.01	$234.00	$234.00
Purchase #2	$161.87	12.541%	$182.1701	$182.17	$182.15	$182.20
Purchase #3	$188.26	4.373%	$196.4926	$196.49	$196.50	$196.50
Purchase #4	$193.53	6.376%	$205.8695	$205.87	$205.85	$205.90
Purchase #5	$145.74	10.541%	$161.1025	$161.10	$161.10	$161.10
Purchase #6	$141.59	13.327%	$160.4597	$160.46	$160.45	$160.50
Purchase #7	$91.59	13.106%	$103.5938	$103.59	$103.60	$103.60
7 purchase totals =	$1,140.15		$1,243.6978	$1,243.69	$1,243.65	$1,243.80