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	$106.77	11.466%	$119.0122	$119.01	$119.00	$119.00
Purchase #2	$129.60	11.650%	$144.6984	$144.70	$144.70	$144.70
Purchase #3	$66.50	7.159%	$71.2607	$71.26	$71.25	$71.30
Purchase #4	$70.97	7.139%	$76.0365	$76.04	$76.05	$76.00
Purchase #5	$134.66	6.145%	$142.9349	$142.93	$142.95	$142.90
Purchase #6	$223.52	12.105%	$250.5771	$250.58	$250.60	$250.60
Purchase #7	$236.33	10.823%	$261.908	$261.91	$261.90	$261.90
7 purchase totals =	$968.35		$1,066.4278	$1,066.43	$1,066.45	$1,066.40