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	$152.45	7.514%	$163.9051	$163.91	$163.90	$163.90
Purchase #2	$168.31	6.305%	$178.9219	$178.92	$178.90	$178.90
Purchase #3	$195.42	13.214%	$221.2428	$221.24	$221.25	$221.20
Purchase #4	$91.61	9.593%	$100.3981	$100.40	$100.40	$100.40
Purchase #5	$183.35	4.330%	$191.2891	$191.29	$191.30	$191.30
Purchase #6	$62.69	13.855%	$71.3757	$71.38	$71.40	$71.40
Purchase #7	$164.67	13.837%	$187.4554	$187.46	$187.45	$187.50
7 purchase totals =	$1,018.50		$1,114.5881	$1,114.60	$1,114.60	$1,114.60