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	$95.84	4.464%	$100.1183	$100.12	$100.10	$100.10
Purchase #2	$29.77	4.336%	$31.0608	$31.06	$31.05	$31.10
Purchase #3	$183.37	7.354%	$196.855	$196.86	$196.85	$196.90
Purchase #4	$115.76	13.669%	$131.5832	$131.58	$131.60	$131.60
Purchase #5	$117.39	7.582%	$126.2905	$126.29	$126.30	$126.30
Purchase #6	$128.73	6.218%	$136.7344	$136.73	$136.75	$136.70
Purchase #7	$153.30	3.409%	$158.526	$158.53	$158.55	$158.50
7 purchase totals =	$824.16		$881.1682	$881.17	$881.20	$881.20