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	$128.78	12.472%	$144.8414	$144.84	$144.85	$144.80
Purchase #2	$204.76	5.632%	$216.2921	$216.29	$216.30	$216.30
Purchase #3	$19.36	9.124%	$21.1264	$21.13	$21.15	$21.10
Purchase #4	$6.87	9.636%	$7.532	$7.53	$7.55	$7.50
Purchase #5	$140.45	3.172%	$144.9051	$144.91	$144.90	$144.90
Purchase #6	$47.75	10.726%	$52.8717	$52.87	$52.85	$52.90
Purchase #7	$182.38	7.586%	$196.2153	$196.22	$196.20	$196.20
7 purchase totals =	$730.35		$783.7840	$783.79	$783.80	$783.70