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	$89.50	10.423%	$98.8286	$98.83	$98.85	$98.80
Purchase #2	$17.74	4.181%	$18.4817	$18.48	$18.50	$18.50
Purchase #3	$105.31	6.521%	$112.1773	$112.18	$112.20	$112.20
Purchase #4	$114.36	11.421%	$127.4211	$127.42	$127.40	$127.40
Purchase #5	$191.76	10.572%	$212.0329	$212.03	$212.05	$212.00
Purchase #6	$115.85	9.432%	$126.777	$126.78	$126.80	$126.80
Purchase #7	$154.71	13.386%	$175.4195	$175.42	$175.40	$175.40
7 purchase totals =	$789.23		$871.1381	$871.14	$871.20	$871.10