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	$72.44	13.719%	$82.378	$82.38	$82.40	$82.40
Purchase #2	$90.56	13.805%	$103.0618	$103.06	$103.05	$103.10
Purchase #3	$65.44	9.256%	$71.4971	$71.50	$71.50	$71.50
Purchase #4	$22.39	8.589%	$24.3131	$24.31	$24.30	$24.30
Purchase #5	$240.27	5.541%	$253.5834	$253.58	$253.60	$253.60
Purchase #6	$10.64	8.810%	$11.5774	$11.58	$11.60	$11.60
Purchase #7	$175.56	6.857%	$187.5981	$187.60	$187.60	$187.60
7 purchase totals =	$677.30		$734.0089	$734.01	$734.05	$734.10