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	$127.38	7.727%	$137.2227	$137.22	$137.20	$137.20
Purchase #2	$87.75	13.866%	$99.9174	$99.92	$99.90	$99.90
Purchase #3	$185.44	8.206%	$200.6572	$200.66	$200.65	$200.70
Purchase #4	$171.53	8.762%	$186.5595	$186.56	$186.55	$186.60
Purchase #5	$117.74	7.479%	$126.5458	$126.55	$126.55	$126.50
Purchase #6	$52.66	5.446%	$55.5279	$55.53	$55.55	$55.50
Purchase #7	$219.52	10.152%	$241.8057	$241.81	$241.80	$241.80
7 purchase totals =	$962.02		$1,048.2362	$1,048.25	$1,048.20	$1,048.20