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	$90.82	8.321%	$98.3771	$98.38	$98.40	$98.40
Purchase #2	$12.26	5.594%	$12.9458	$12.95	$12.95	$12.90
Purchase #3	$90.66	4.255%	$94.5176	$94.52	$94.50	$94.50
Purchase #4	$137.54	5.870%	$145.6136	$145.61	$145.60	$145.60
Purchase #5	$171.81	8.787%	$186.9069	$186.91	$186.90	$186.90
Purchase #6	$230.70	10.746%	$255.491	$255.49	$255.50	$255.50
Purchase #7	$222.76	5.387%	$234.7601	$234.76	$234.75	$234.80
7 purchase totals =	$956.55		$1,028.6121	$1,028.62	$1,028.60	$1,028.60