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	$52.33	11.274%	$58.2297	$58.23	$58.25	$58.20
Purchase #2	$26.54	11.226%	$29.5194	$29.52	$29.50	$29.50
Purchase #3	$38.51	10.577%	$42.5832	$42.58	$42.60	$42.60
Purchase #4	$158.53	3.853%	$164.6382	$164.64	$164.65	$164.60
Purchase #5	$235.45	11.287%	$262.0252	$262.03	$262.05	$262.00
Purchase #6	$229.84	12.782%	$259.2181	$259.22	$259.20	$259.20
Purchase #7	$234.87	12.793%	$264.9169	$264.92	$264.90	$264.90
7 purchase totals =	$976.07		$1,081.1307	$1,081.14	$1,081.15	$1,081.00