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	$174.95	8.688%	$190.1497	$190.15	$190.15	$190.10
Purchase #2	$26.49	9.385%	$28.9761	$28.98	$29.00	$29.00
Purchase #3	$92.28	11.718%	$103.0934	$103.09	$103.10	$103.10
Purchase #4	$77.84	10.808%	$86.2529	$86.25	$86.25	$86.30
Purchase #5	$162.66	13.617%	$184.8094	$184.81	$184.80	$184.80
Purchase #6	$71.62	10.138%	$78.8808	$78.88	$78.90	$78.90
Purchase #7	$133.60	12.527%	$150.3361	$150.34	$150.35	$150.30
7 purchase totals =	$739.44		$822.4984	$822.50	$822.55	$822.50