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	$140.29	8.446%	$152.1389	$152.14	$152.15	$152.10
Purchase #2	$111.74	11.427%	$124.5085	$124.51	$124.50	$124.50
Purchase #3	$173.29	13.798%	$197.2006	$197.20	$197.20	$197.20
Purchase #4	$109.59	10.233%	$120.8043	$120.80	$120.80	$120.80
Purchase #5	$161.37	10.574%	$178.4333	$178.43	$178.45	$178.40
Purchase #6	$164.43	13.445%	$186.5376	$186.54	$186.55	$186.50
Purchase #7	$136.54	3.514%	$141.338	$141.34	$141.35	$141.30
7 purchase totals =	$997.25		$1,100.9612	$1,100.96	$1,101.00	$1,100.80