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	$116.45	9.808%	$127.8714	$127.87	$127.85	$127.90
Purchase #2	$237.89	7.708%	$256.2266	$256.23	$256.25	$256.20
Purchase #3	$231.75	10.241%	$255.4835	$255.48	$255.50	$255.50
Purchase #4	$177.69	12.222%	$199.4073	$199.41	$199.40	$199.40
Purchase #5	$101.53	6.467%	$108.0959	$108.10	$108.10	$108.10
Purchase #6	$48.26	9.616%	$52.9007	$52.90	$52.90	$52.90
Purchase #7	$153.61	9.748%	$168.5839	$168.58	$168.60	$168.60
7 purchase totals =	$1,067.18		$1,168.5693	$1,168.57	$1,168.60	$1,168.60