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	$33.81	5.562%	$35.6905	$35.69	$35.70	$35.70
Purchase #2	$158.27	5.321%	$166.6915	$166.69	$166.70	$166.70
Purchase #3	$200.34	10.583%	$221.542	$221.54	$221.55	$221.50
Purchase #4	$145.54	10.510%	$160.8363	$160.84	$160.85	$160.80
Purchase #5	$59.81	7.501%	$64.2963	$64.30	$64.30	$64.30
Purchase #6	$96.40	9.706%	$105.7566	$105.76	$105.75	$105.80
Purchase #7	$132.84	10.529%	$146.8267	$146.83	$146.85	$146.80
7 purchase totals =	$827.01		$901.6399	$901.65	$901.70	$901.60