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	$33.82	6.524%	$36.0264	$36.03	$36.05	$36.00
Purchase #2	$23.93	8.237%	$25.9011	$25.90	$25.90	$25.90
Purchase #3	$151.50	6.194%	$160.8839	$160.88	$160.90	$160.90
Purchase #4	$13.32	10.563%	$14.727	$14.73	$14.75	$14.70
Purchase #5	$97.38	12.334%	$109.3908	$109.39	$109.40	$109.40
Purchase #6	$173.95	12.764%	$196.153	$196.15	$196.15	$196.20
Purchase #7	$248.59	8.421%	$269.5238	$269.52	$269.50	$269.50
7 purchase totals =	$742.49		$812.6060	$812.60	$812.65	$812.60