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	$186.56	6.214%	$198.1528	$198.15	$198.15	$198.20
Purchase #2	$134.70	11.856%	$150.67	$150.67	$150.65	$150.70
Purchase #3	$42.44	9.157%	$46.3262	$46.33	$46.35	$46.30
Purchase #4	$64.56	11.656%	$72.0851	$72.09	$72.10	$72.10
Purchase #5	$181.42	7.237%	$194.5494	$194.55	$194.55	$194.50
Purchase #6	$236.72	3.584%	$245.204	$245.20	$245.20	$245.20
Purchase #7	$164.43	5.466%	$173.4177	$173.42	$173.40	$173.40
7 purchase totals =	$1,010.83		$1,080.4052	$1,080.41	$1,080.40	$1,080.40