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	$244.41	7.112%	$261.7924	$261.79	$261.80	$261.80
Purchase #2	$49.75	8.212%	$53.8355	$53.84	$53.85	$53.80
Purchase #3	$178.88	9.850%	$196.4997	$196.50	$196.50	$196.50
Purchase #4	$113.76	8.492%	$123.4205	$123.42	$123.40	$123.40
Purchase #5	$156.37	3.172%	$161.3301	$161.33	$161.35	$161.30
Purchase #6	$204.81	5.163%	$215.3843	$215.38	$215.40	$215.40
Purchase #7	$11.98	11.591%	$13.3686	$13.37	$13.35	$13.40
7 purchase totals =	$959.96		$1,025.6311	$1,025.63	$1,025.65	$1,025.60