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	$65.42	9.431%	$71.5898	$71.59	$71.60	$71.60
Purchase #2	$102.38	9.454%	$112.059	$112.06	$112.05	$112.10
Purchase #3	$38.44	3.102%	$39.6324	$39.63	$39.65	$39.60
Purchase #4	$58.93	6.405%	$62.7045	$62.70	$62.70	$62.70
Purchase #5	$53.63	7.434%	$57.6169	$57.62	$57.60	$57.60
Purchase #6	$244.53	8.302%	$264.8309	$264.83	$264.85	$264.80
Purchase #7	$100.48	4.744%	$105.2468	$105.25	$105.25	$105.20
7 purchase totals =	$663.81		$713.6803	$713.68	$713.70	$713.60