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	$65.60	10.184%	$72.2807	$72.28	$72.30	$72.30
Purchase #2	$15.91	10.430%	$17.5694	$17.57	$17.55	$17.60
Purchase #3	$51.26	9.455%	$56.1066	$56.11	$56.10	$56.10
Purchase #4	$55.61	13.257%	$62.9822	$62.98	$63.00	$63.00
Purchase #5	$219.33	10.486%	$242.3289	$242.33	$242.35	$242.30
Purchase #6	$12.70	7.612%	$13.6667	$13.67	$13.65	$13.70
Purchase #7	$167.43	10.799%	$185.5108	$185.51	$185.50	$185.50
7 purchase totals =	$587.84		$650.4453	$650.45	$650.45	$650.50