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	$211.58	10.819%	$234.4708	$234.47	$234.45	$234.50
Purchase #2	$190.61	9.200%	$208.1461	$208.15	$208.15	$208.10
Purchase #3	$153.41	9.743%	$168.3567	$168.36	$168.35	$168.40
Purchase #4	$56.94	10.817%	$63.0992	$63.10	$63.10	$63.10
Purchase #5	$27.32	4.355%	$28.5098	$28.51	$28.50	$28.50
Purchase #6	$66.27	9.546%	$72.5961	$72.60	$72.60	$72.60
Purchase #7	$194.26	13.768%	$221.0057	$221.01	$221.00	$221.00
7 purchase totals =	$900.39		$996.1844	$996.20	$996.15	$996.20