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	$66.92	8.366%	$72.5185	$72.52	$72.50	$72.50
Purchase #2	$99.89	8.847%	$108.7273	$108.73	$108.75	$108.70
Purchase #3	$80.52	3.626%	$83.4397	$83.44	$83.45	$83.40
Purchase #4	$165.60	12.254%	$185.8926	$185.89	$185.90	$185.90
Purchase #5	$54.86	8.396%	$59.466	$59.47	$59.45	$59.50
Purchase #6	$57.48	10.240%	$63.366	$63.37	$63.35	$63.40
Purchase #7	$24.46	13.411%	$27.7403	$27.74	$27.75	$27.70
7 purchase totals =	$549.73		$601.1504	$601.16	$601.15	$601.10