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	$150.46	11.478%	$167.7298	$167.73	$167.75	$167.70
Purchase #2	$161.38	7.684%	$173.7804	$173.78	$173.80	$173.80
Purchase #3	$21.91	13.675%	$24.9062	$24.91	$24.90	$24.90
Purchase #4	$55.44	13.423%	$62.8817	$62.88	$62.90	$62.90
Purchase #5	$159.31	3.235%	$164.4637	$164.46	$164.45	$164.50
Purchase #6	$79.55	3.142%	$82.0495	$82.05	$82.05	$82.00
Purchase #7	$61.90	7.845%	$66.7561	$66.76	$66.75	$66.80
7 purchase totals =	$689.95		$742.5674	$742.57	$742.60	$742.60