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	$80.59	7.371%	$86.5303	$86.53	$86.55	$86.50
Purchase #2	$62.98	7.126%	$67.468	$67.47	$67.45	$67.50
Purchase #3	$200.74	9.272%	$219.3526	$219.35	$219.35	$219.40
Purchase #4	$142.28	7.370%	$152.766	$152.77	$152.75	$152.80
Purchase #5	$138.79	10.236%	$152.9965	$153.00	$153.00	$153.00
Purchase #6	$21.50	13.383%	$24.3773	$24.38	$24.40	$24.40
Purchase #7	$249.45	4.564%	$260.8349	$260.83	$260.85	$260.80
7 purchase totals =	$896.33		$964.3256	$964.33	$964.35	$964.40