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	$149.26	12.263%	$167.5638	$167.56	$167.55	$167.60
Purchase #2	$108.38	7.117%	$116.0934	$116.09	$116.10	$116.10
Purchase #3	$160.84	7.866%	$173.4917	$173.49	$173.50	$173.50
Purchase #4	$168.80	13.262%	$191.1863	$191.19	$191.20	$191.20
Purchase #5	$164.37	8.556%	$178.4335	$178.43	$178.45	$178.40
Purchase #6	$137.91	12.345%	$154.935	$154.94	$154.95	$154.90
Purchase #7	$55.59	7.661%	$59.8487	$59.85	$59.85	$59.80
7 purchase totals =	$945.15		$1,041.5524	$1,041.55	$1,041.60	$1,041.50