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	$122.92	3.730%	$127.5049	$127.50	$127.50	$127.50
Purchase #2	$91.96	7.206%	$98.5866	$98.59	$98.60	$98.60
Purchase #3	$166.61	12.644%	$187.6762	$187.68	$187.70	$187.70
Purchase #4	$108.36	10.171%	$119.3813	$119.38	$119.40	$119.40
Purchase #5	$156.45	10.238%	$172.4674	$172.47	$172.45	$172.50
Purchase #6	$191.69	4.782%	$200.8566	$200.86	$200.85	$200.90
Purchase #7	$56.88	3.804%	$59.0437	$59.04	$59.05	$59.00
7 purchase totals =	$894.87		$965.5167	$965.52	$965.55	$965.60