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	$113.88	3.496%	$117.8612	$117.86	$117.85	$117.90
Purchase #2	$171.94	8.693%	$186.8867	$186.89	$186.90	$186.90
Purchase #3	$71.55	11.660%	$79.8927	$79.89	$79.90	$79.90
Purchase #4	$128.30	12.237%	$144.0001	$144.00	$144.00	$144.00
Purchase #5	$163.42	13.252%	$185.0764	$185.08	$185.10	$185.10
Purchase #6	$19.43	4.705%	$20.3442	$20.34	$20.35	$20.30
Purchase #7	$151.39	6.325%	$160.9654	$160.97	$160.95	$161.00
7 purchase totals =	$819.91		$895.0267	$895.03	$895.05	$895.10