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	$183.29	3.239%	$189.2268	$189.23	$189.25	$189.20
Purchase #2	$170.61	10.109%	$187.857	$187.86	$187.85	$187.90
Purchase #3	$95.99	7.306%	$103.003	$103.00	$103.00	$103.00
Purchase #4	$49.82	8.314%	$53.962	$53.96	$53.95	$54.00
Purchase #5	$240.80	11.243%	$267.8731	$267.87	$267.85	$267.90
Purchase #6	$25.89	6.691%	$27.6223	$27.62	$27.60	$27.60
Purchase #7	$179.72	6.813%	$191.9643	$191.96	$191.95	$192.00
7 purchase totals =	$946.12		$1,021.5085	$1,021.50	$1,021.45	$1,021.60