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	$240.81	5.695%	$254.5241	$254.52	$254.50	$254.50
Purchase #2	$103.68	12.374%	$116.5094	$116.51	$116.50	$116.50
Purchase #3	$77.79	7.267%	$83.443	$83.44	$83.45	$83.40
Purchase #4	$6.48	6.313%	$6.8891	$6.89	$6.90	$6.90
Purchase #5	$139.78	9.739%	$153.3932	$153.39	$153.40	$153.40
Purchase #6	$120.54	4.673%	$126.1728	$126.17	$126.15	$126.20
Purchase #7	$241.49	7.459%	$259.5027	$259.50	$259.50	$259.50
7 purchase totals =	$930.57		$1,000.4343	$1,000.42	$1,000.40	$1,000.40