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	$105.45	3.805%	$109.4624	$109.46	$109.45	$109.50
Purchase #2	$45.54	5.455%	$48.0242	$48.02	$48.00	$48.00
Purchase #3	$17.39	6.596%	$18.537	$18.54	$18.55	$18.50
Purchase #4	$69.31	11.543%	$77.3105	$77.31	$77.30	$77.30
Purchase #5	$69.59	4.296%	$72.5796	$72.58	$72.60	$72.60
Purchase #6	$221.60	12.361%	$248.992	$248.99	$249.00	$249.00
Purchase #7	$84.59	8.455%	$91.7421	$91.74	$91.75	$91.70
7 purchase totals =	$613.47		$666.6478	$666.64	$666.65	$666.60