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	$75.90	12.446%	$85.3465	$85.35	$85.35	$85.30
Purchase #2	$85.30	5.582%	$90.0614	$90.06	$90.05	$90.10
Purchase #3	$80.99	5.155%	$85.165	$85.17	$85.15	$85.20
Purchase #4	$16.96	10.583%	$18.7549	$18.75	$18.75	$18.80
Purchase #5	$204.81	3.823%	$212.6399	$212.64	$212.65	$212.60
Purchase #6	$209.77	12.390%	$235.7605	$235.76	$235.75	$235.80
Purchase #7	$40.77	10.848%	$45.1927	$45.19	$45.20	$45.20
7 purchase totals =	$714.50		$772.9209	$772.92	$772.90	$773.00