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	$27.32	8.564%	$29.6597	$29.66	$29.65	$29.70
Purchase #2	$96.61	3.396%	$99.8909	$99.89	$99.90	$99.90
Purchase #3	$188.79	3.262%	$194.9483	$194.95	$194.95	$194.90
Purchase #4	$73.62	3.242%	$76.0068	$76.01	$76.00	$76.00
Purchase #5	$139.85	4.773%	$146.525	$146.53	$146.55	$146.50
Purchase #6	$11.40	8.663%	$12.3876	$12.39	$12.40	$12.40
Purchase #7	$147.35	5.115%	$154.887	$154.89	$154.90	$154.90
7 purchase totals =	$684.94		$714.3053	$714.32	$714.35	$714.30