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	$236.54	9.554%	$259.139	$259.14	$259.15	$259.10
Purchase #2	$152.69	7.504%	$164.1479	$164.15	$164.15	$164.10
Purchase #3	$52.44	7.776%	$56.5177	$56.52	$56.50	$56.50
Purchase #4	$246.61	4.783%	$258.4054	$258.41	$258.40	$258.40
Purchase #5	$223.88	8.750%	$243.4695	$243.47	$243.45	$243.50
Purchase #6	$47.43	11.506%	$52.8873	$52.89	$52.90	$52.90
Purchase #7	$212.74	11.413%	$237.02	$237.02	$237.00	$237.00
7 purchase totals =	$1,172.33		$1,271.5868	$1,271.60	$1,271.55	$1,271.50