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	$95.83	4.748%	$100.38	$100.38	$100.40	$100.40
Purchase #2	$67.85	10.539%	$75.0007	$75.00	$75.00	$75.00
Purchase #3	$81.62	6.214%	$86.6919	$86.69	$86.70	$86.70
Purchase #4	$131.27	10.675%	$145.2831	$145.28	$145.30	$145.30
Purchase #5	$87.31	13.868%	$99.4182	$99.42	$99.40	$99.40
Purchase #6	$126.46	3.639%	$131.0619	$131.06	$131.05	$131.10
Purchase #7	$36.89	7.854%	$39.7873	$39.79	$39.80	$39.80
7 purchase totals =	$627.23		$677.6231	$677.62	$677.65	$677.70