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	$52.28	4.480%	$54.6221	$54.62	$54.60	$54.60
Purchase #2	$104.59	6.660%	$111.5557	$111.56	$111.55	$111.60
Purchase #3	$91.79	13.862%	$104.5139	$104.51	$104.50	$104.50
Purchase #4	$173.80	13.135%	$196.6286	$196.63	$196.65	$196.60
Purchase #5	$77.33	11.257%	$86.035	$86.04	$86.05	$86.00
Purchase #6	$142.25	4.485%	$148.6299	$148.63	$148.65	$148.60
Purchase #7	$203.62	9.173%	$222.2981	$222.30	$222.30	$222.30
7 purchase totals =	$845.66		$924.2833	$924.29	$924.30	$924.20