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	$14.61	5.473%	$15.4096	$15.41	$15.40	$15.40
Purchase #2	$32.39	3.223%	$33.4339	$33.43	$33.45	$33.40
Purchase #3	$28.81	13.134%	$32.5939	$32.59	$32.60	$32.60
Purchase #4	$33.49	12.844%	$37.7915	$37.79	$37.80	$37.80
Purchase #5	$140.42	3.249%	$144.9822	$144.98	$145.00	$145.00
Purchase #6	$49.56	13.745%	$56.372	$56.37	$56.35	$56.40
Purchase #7	$234.50	6.160%	$248.9452	$248.95	$248.95	$248.90
7 purchase totals =	$533.78		$569.5283	$569.52	$569.55	$569.50