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	$118.64	7.472%	$127.5048	$127.50	$127.50	$127.50
Purchase #2	$161.50	12.352%	$181.4485	$181.45	$181.45	$181.40
Purchase #3	$112.26	12.397%	$126.1769	$126.18	$126.20	$126.20
Purchase #4	$100.98	10.393%	$111.4749	$111.47	$111.45	$111.50
Purchase #5	$202.47	6.460%	$215.5496	$215.55	$215.55	$215.50
Purchase #6	$47.39	6.428%	$50.4362	$50.44	$50.45	$50.40
Purchase #7	$86.71	7.326%	$93.0624	$93.06	$93.05	$93.10
7 purchase totals =	$829.95		$905.6533	$905.65	$905.65	$905.60