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	$29.87	12.575%	$33.6262	$33.63	$33.65	$33.60
Purchase #2	$217.25	3.658%	$225.197	$225.20	$225.20	$225.20
Purchase #3	$122.45	8.843%	$133.2783	$133.28	$133.30	$133.30
Purchase #4	$117.39	8.549%	$127.4257	$127.43	$127.45	$127.40
Purchase #5	$159.76	12.281%	$179.3801	$179.38	$179.40	$179.40
Purchase #6	$181.60	10.245%	$200.2049	$200.20	$200.20	$200.20
Purchase #7	$187.59	4.590%	$196.2004	$196.20	$196.20	$196.20
7 purchase totals =	$1,015.91		$1,095.3126	$1,095.32	$1,095.40	$1,095.30