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	$68.91	4.272%	$71.8538	$71.85	$71.85	$71.90
Purchase #2	$24.79	9.638%	$27.1793	$27.18	$27.20	$27.20
Purchase #3	$49.75	3.628%	$51.5549	$51.55	$51.55	$51.60
Purchase #4	$144.28	9.560%	$158.0732	$158.07	$158.05	$158.10
Purchase #5	$135.88	13.389%	$154.073	$154.07	$154.05	$154.10
Purchase #6	$172.39	7.455%	$185.2417	$185.24	$185.25	$185.20
Purchase #7	$134.69	4.549%	$140.817	$140.82	$140.80	$140.80
7 purchase totals =	$730.69		$788.7929	$788.78	$788.75	$788.90