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	$150.32	4.189%	$156.6169	$156.62	$156.60	$156.60
Purchase #2	$19.26	11.672%	$21.508	$21.51	$21.50	$21.50
Purchase #3	$8.74	12.727%	$9.8523	$9.85	$9.85	$9.90
Purchase #4	$85.92	12.698%	$96.8301	$96.83	$96.85	$96.80
Purchase #5	$37.89	11.722%	$42.3315	$42.33	$42.35	$42.30
Purchase #6	$196.28	12.219%	$220.2635	$220.26	$220.25	$220.30
Purchase #7	$130.47	11.574%	$145.5706	$145.57	$145.55	$145.60
7 purchase totals =	$628.88		$692.9729	$692.97	$692.95	$693.00