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	$90.82	8.618%	$98.6469	$98.65	$98.65	$98.60
Purchase #2	$54.70	6.450%	$58.2282	$58.23	$58.25	$58.20
Purchase #3	$17.35	9.253%	$18.9554	$18.96	$18.95	$19.00
Purchase #4	$205.36	10.644%	$227.2185	$227.22	$227.20	$227.20
Purchase #5	$52.39	12.627%	$59.0053	$59.01	$59.00	$59.00
Purchase #6	$235.89	8.274%	$255.4075	$255.41	$255.40	$255.40
Purchase #7	$206.56	13.698%	$234.8546	$234.85	$234.85	$234.90
7 purchase totals =	$863.07		$952.3164	$952.33	$952.30	$952.30