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	$174.39	12.457%	$196.1138	$196.11	$196.10	$196.10
Purchase #2	$112.52	9.281%	$122.963	$122.96	$122.95	$123.00
Purchase #3	$36.61	3.509%	$37.8946	$37.89	$37.90	$37.90
Purchase #4	$28.55	3.534%	$29.559	$29.56	$29.55	$29.60
Purchase #5	$58.75	8.315%	$63.6351	$63.64	$63.65	$63.60
Purchase #6	$113.95	4.346%	$118.9023	$118.90	$118.90	$118.90
Purchase #7	$48.33	10.813%	$53.5559	$53.56	$53.55	$53.60
7 purchase totals =	$573.10		$622.6237	$622.62	$622.60	$622.70