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	$210.32	13.771%	$239.2832	$239.28	$239.30	$239.30
Purchase #2	$217.31	12.498%	$244.4694	$244.47	$244.45	$244.50
Purchase #3	$49.25	10.253%	$54.2996	$54.30	$54.30	$54.30
Purchase #4	$48.26	6.226%	$51.2647	$51.26	$51.25	$51.30
Purchase #5	$177.27	10.612%	$196.0819	$196.08	$196.10	$196.10
Purchase #6	$150.43	11.607%	$167.8904	$167.89	$167.90	$167.90
Purchase #7	$116.38	11.661%	$129.9511	$129.95	$129.95	$130.00
7 purchase totals =	$969.22		$1,083.2403	$1,083.23	$1,083.25	$1,083.40