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	$119.87	4.518%	$125.2857	$125.29	$125.30	$125.30
Purchase #2	$32.79	12.620%	$36.9281	$36.93	$36.95	$36.90
Purchase #3	$116.95	12.218%	$131.239	$131.24	$131.25	$131.20
Purchase #4	$98.52	11.138%	$109.4932	$109.49	$109.50	$109.50
Purchase #5	$205.30	9.261%	$224.3128	$224.31	$224.30	$224.30
Purchase #6	$172.92	13.405%	$196.0999	$196.10	$196.10	$196.10
Purchase #7	$52.97	8.705%	$57.581	$57.58	$57.60	$57.60
7 purchase totals =	$799.32		$880.9397	$880.94	$881.00	$880.90