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	$228.85	8.185%	$247.5814	$247.58	$247.60	$247.60
Purchase #2	$188.36	4.221%	$196.3107	$196.31	$196.30	$196.30
Purchase #3	$168.88	7.162%	$180.9752	$180.98	$181.00	$181.00
Purchase #4	$80.95	12.202%	$90.8275	$90.83	$90.85	$90.80
Purchase #5	$179.95	11.773%	$201.1355	$201.14	$201.15	$201.10
Purchase #6	$198.45	12.804%	$223.8595	$223.86	$223.85	$223.90
Purchase #7	$120.55	10.754%	$133.5139	$133.51	$133.50	$133.50
7 purchase totals =	$1,165.99		$1,274.2037	$1,274.21	$1,274.25	$1,274.20