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	$45.62	3.572%	$47.2495	$47.25	$47.25	$47.20
Purchase #2	$150.80	11.137%	$167.5946	$167.59	$167.60	$167.60
Purchase #3	$77.85	5.451%	$82.0936	$82.09	$82.10	$82.10
Purchase #4	$148.50	13.543%	$168.6114	$168.61	$168.60	$168.60
Purchase #5	$132.71	12.436%	$149.2138	$149.21	$149.20	$149.20
Purchase #6	$18.36	10.614%	$20.3087	$20.31	$20.30	$20.30
Purchase #7	$143.31	12.326%	$160.9744	$160.97	$160.95	$161.00
7 purchase totals =	$717.15		$796.0460	$796.03	$796.00	$796.00