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	$42.65	5.398%	$44.9522	$44.95	$44.95	$45.00
Purchase #2	$92.48	12.787%	$104.3054	$104.31	$104.30	$104.30
Purchase #3	$151.82	11.212%	$168.8421	$168.84	$168.85	$168.80
Purchase #4	$74.38	7.393%	$79.8789	$79.88	$79.90	$79.90
Purchase #5	$98.29	13.526%	$111.5847	$111.58	$111.60	$111.60
Purchase #6	$84.62	7.453%	$90.9267	$90.93	$90.95	$90.90
Purchase #7	$173.89	7.860%	$187.5578	$187.56	$187.55	$187.60
7 purchase totals =	$718.13		$788.0478	$788.05	$788.10	$788.10