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	$241.40	7.333%	$259.1019	$259.10	$259.10	$259.10
Purchase #2	$174.69	5.279%	$183.9119	$183.91	$183.90	$183.90
Purchase #3	$164.29	6.659%	$175.2301	$175.23	$175.25	$175.20
Purchase #4	$113.68	7.750%	$122.4902	$122.49	$122.50	$122.50
Purchase #5	$208.71	4.693%	$218.5048	$218.50	$218.50	$218.50
Purchase #6	$147.63	11.376%	$164.4244	$164.42	$164.40	$164.40
Purchase #7	$66.80	8.823%	$72.6938	$72.69	$72.70	$72.70
7 purchase totals =	$1,117.20		$1,196.3571	$1,196.34	$1,196.35	$1,196.30