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	$191.92	6.306%	$204.0225	$204.02	$204.00	$204.00
Purchase #2	$119.29	10.714%	$132.0707	$132.07	$132.05	$132.10
Purchase #3	$231.58	9.418%	$253.3902	$253.39	$253.40	$253.40
Purchase #4	$170.56	4.719%	$178.6087	$178.61	$178.60	$178.60
Purchase #5	$41.98	3.398%	$43.4065	$43.41	$43.40	$43.40
Purchase #6	$94.96	11.193%	$105.5889	$105.59	$105.60	$105.60
Purchase #7	$152.55	5.130%	$160.3758	$160.38	$160.40	$160.40
7 purchase totals =	$1,002.84		$1,077.4633	$1,077.47	$1,077.45	$1,077.50