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	$134.32	6.165%	$142.6008	$142.60	$142.60	$142.60
Purchase #2	$144.49	7.631%	$155.516	$155.52	$155.50	$155.50
Purchase #3	$143.68	11.445%	$160.1242	$160.12	$160.10	$160.10
Purchase #4	$232.61	11.468%	$259.2857	$259.29	$259.30	$259.30
Purchase #5	$74.96	11.535%	$83.6066	$83.61	$83.60	$83.60
Purchase #6	$179.26	4.822%	$187.9039	$187.90	$187.90	$187.90
Purchase #7	$24.57	3.663%	$25.47	$25.47	$25.45	$25.50
7 purchase totals =	$933.89		$1,014.5072	$1,014.51	$1,014.45	$1,014.50