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	$77.87	7.637%	$83.8169	$83.82	$83.80	$83.80
Purchase #2	$66.49	7.605%	$71.5466	$71.55	$71.55	$71.50
Purchase #3	$103.46	10.455%	$114.2767	$114.28	$114.30	$114.30
Purchase #4	$40.33	8.233%	$43.6504	$43.65	$43.65	$43.70
Purchase #5	$84.84	12.635%	$95.5595	$95.56	$95.55	$95.60
Purchase #6	$178.30	7.582%	$191.8187	$191.82	$191.80	$191.80
Purchase #7	$95.42	13.417%	$108.2225	$108.22	$108.20	$108.20
7 purchase totals =	$646.71		$708.8913	$708.90	$708.85	$708.90