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	$111.70	10.373%	$123.2866	$123.29	$123.30	$123.30
Purchase #2	$186.27	9.461%	$203.893	$203.89	$203.90	$203.90
Purchase #3	$122.98	3.208%	$126.9252	$126.93	$126.95	$126.90
Purchase #4	$203.69	6.379%	$216.6834	$216.68	$216.70	$216.70
Purchase #5	$93.65	7.314%	$100.4996	$100.50	$100.50	$100.50
Purchase #6	$246.64	3.172%	$254.4634	$254.46	$254.45	$254.50
Purchase #7	$47.35	9.487%	$51.8421	$51.84	$51.85	$51.80
7 purchase totals =	$1,012.28		$1,077.5933	$1,077.59	$1,077.65	$1,077.60