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	$85.60	12.152%	$96.0021	$96.00	$96.00	$96.00
Purchase #2	$41.61	4.632%	$43.5374	$43.54	$43.55	$43.50
Purchase #3	$16.95	6.684%	$18.0829	$18.08	$18.10	$18.10
Purchase #4	$184.47	8.693%	$200.506	$200.51	$200.50	$200.50
Purchase #5	$5.40	7.163%	$5.7868	$5.79	$5.80	$5.80
Purchase #6	$29.89	9.332%	$32.6793	$32.68	$32.70	$32.70
Purchase #7	$167.57	10.691%	$185.4849	$185.48	$185.50	$185.50
7 purchase totals =	$531.49		$582.0794	$582.08	$582.15	$582.10