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	$64.66	11.415%	$72.0409	$72.04	$72.05	$72.00
Purchase #2	$181.82	3.176%	$187.5946	$187.59	$187.60	$187.60
Purchase #3	$17.52	4.651%	$18.3349	$18.33	$18.35	$18.30
Purchase #4	$17.36	8.847%	$18.8958	$18.90	$18.90	$18.90
Purchase #5	$182.40	7.704%	$196.4521	$196.45	$196.45	$196.50
Purchase #6	$77.94	11.401%	$86.8259	$86.83	$86.85	$86.80
Purchase #7	$121.75	3.820%	$126.4009	$126.40	$126.40	$126.40
7 purchase totals =	$663.45		$706.5451	$706.54	$706.60	$706.50