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	$99.51	8.651%	$108.1186	$108.12	$108.10	$108.10
Purchase #2	$149.89	5.577%	$158.2494	$158.25	$158.25	$158.20
Purchase #3	$59.69	3.772%	$61.9415	$61.94	$61.95	$61.90
Purchase #4	$162.77	10.672%	$180.1408	$180.14	$180.15	$180.10
Purchase #5	$189.28	8.470%	$205.312	$205.31	$205.30	$205.30
Purchase #6	$100.35	11.868%	$112.2595	$112.26	$112.25	$112.30
Purchase #7	$42.76	12.346%	$48.0391	$48.04	$48.05	$48.00
7 purchase totals =	$804.25		$874.0609	$874.06	$874.05	$873.90