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	$189.73	3.704%	$196.7576	$196.76	$196.75	$196.80
Purchase #2	$100.55	4.630%	$105.2055	$105.21	$105.20	$105.20
Purchase #3	$70.64	10.608%	$78.1335	$78.13	$78.15	$78.10
Purchase #4	$18.28	3.146%	$18.8551	$18.86	$18.85	$18.90
Purchase #5	$54.40	5.605%	$57.4491	$57.45	$57.45	$57.40
Purchase #6	$76.87	9.497%	$84.1703	$84.17	$84.15	$84.20
Purchase #7	$35.93	7.401%	$38.5892	$38.59	$38.60	$38.60
7 purchase totals =	$546.40		$579.1603	$579.17	$579.15	$579.20