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	$75.59	13.248%	$85.6042	$85.60	$85.60	$85.60
Purchase #2	$139.44	10.842%	$154.5581	$154.56	$154.55	$154.60
Purchase #3	$99.78	6.780%	$106.5451	$106.55	$106.55	$106.50
Purchase #4	$155.71	6.449%	$165.7517	$165.75	$165.75	$165.80
Purchase #5	$218.52	7.185%	$234.2207	$234.22	$234.20	$234.20
Purchase #6	$166.37	9.291%	$181.8274	$181.83	$181.85	$181.80
Purchase #7	$121.42	10.433%	$134.0877	$134.09	$134.10	$134.10
7 purchase totals =	$976.83		$1,062.5949	$1,062.60	$1,062.60	$1,062.60