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	$178.38	5.750%	$188.6369	$188.64	$188.65	$188.60
Purchase #2	$164.34	4.817%	$172.2563	$172.26	$172.25	$172.30
Purchase #3	$75.47	6.766%	$80.5763	$80.58	$80.60	$80.60
Purchase #4	$63.64	6.641%	$67.8663	$67.87	$67.85	$67.90
Purchase #5	$136.82	11.467%	$152.5091	$152.51	$152.50	$152.50
Purchase #6	$142.35	8.169%	$153.9786	$153.98	$154.00	$154.00
Purchase #7	$239.87	3.259%	$247.6874	$247.69	$247.70	$247.70
7 purchase totals =	$1,000.87		$1,063.5109	$1,063.53	$1,063.55	$1,063.60