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	$191.29	13.593%	$217.292	$217.29	$217.30	$217.30
Purchase #2	$47.88	11.176%	$53.2311	$53.23	$53.25	$53.20
Purchase #3	$122.44	11.214%	$136.1704	$136.17	$136.15	$136.20
Purchase #4	$133.25	7.276%	$142.9453	$142.95	$142.95	$142.90
Purchase #5	$104.72	6.440%	$111.464	$111.46	$111.45	$111.50
Purchase #6	$197.86	3.734%	$205.2481	$205.25	$205.25	$205.20
Purchase #7	$21.78	13.262%	$24.6685	$24.67	$24.65	$24.70
7 purchase totals =	$819.22		$891.0194	$891.02	$891.00	$891.00