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	$204.86	9.260%	$223.83	$223.83	$223.85	$223.80
Purchase #2	$10.32	6.610%	$11.0022	$11.00	$11.00	$11.00
Purchase #3	$166.85	11.843%	$186.61	$186.61	$186.60	$186.60
Purchase #4	$158.84	12.368%	$178.4853	$178.49	$178.50	$178.50
Purchase #5	$172.76	10.339%	$190.6217	$190.62	$190.60	$190.60
Purchase #6	$236.81	9.857%	$260.1524	$260.15	$260.15	$260.20
Purchase #7	$38.56	3.721%	$39.9948	$39.99	$40.00	$40.00
7 purchase totals =	$989.00		$1,090.6964	$1,090.69	$1,090.70	$1,090.70