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	$97.47	5.397%	$102.7305	$102.73	$102.75	$102.70
Purchase #2	$108.60	9.712%	$119.1472	$119.15	$119.15	$119.10
Purchase #3	$119.78	6.451%	$127.507	$127.51	$127.50	$127.50
Purchase #4	$158.41	3.816%	$164.4549	$164.45	$164.45	$164.50
Purchase #5	$175.82	6.671%	$187.549	$187.55	$187.55	$187.50
Purchase #6	$42.58	3.538%	$44.0865	$44.09	$44.10	$44.10
Purchase #7	$7.29	4.301%	$7.6035	$7.60	$7.60	$7.60
7 purchase totals =	$709.95		$753.0786	$753.08	$753.10	$753.00