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	$154.78	8.119%	$167.3466	$167.35	$167.35	$167.30
Purchase #2	$108.65	5.135%	$114.2292	$114.23	$114.25	$114.20
Purchase #3	$100.93	10.750%	$111.78	$111.78	$111.80	$111.80
Purchase #4	$190.85	7.564%	$205.2859	$205.29	$205.30	$205.30
Purchase #5	$238.25	4.584%	$249.1714	$249.17	$249.15	$249.20
Purchase #6	$163.96	3.425%	$169.5756	$169.58	$169.60	$169.60
Purchase #7	$28.96	13.851%	$32.9712	$32.97	$32.95	$33.00
7 purchase totals =	$986.38		$1,050.3599	$1,050.37	$1,050.40	$1,050.40