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	$82.71	12.127%	$92.7402	$92.74	$92.75	$92.70
Purchase #2	$48.84	7.195%	$52.354	$52.35	$52.35	$52.40
Purchase #3	$248.31	13.750%	$282.4526	$282.45	$282.45	$282.50
Purchase #4	$211.31	7.784%	$227.7584	$227.76	$227.75	$227.80
Purchase #5	$116.56	12.633%	$131.285	$131.29	$131.30	$131.30
Purchase #6	$178.34	9.801%	$195.8191	$195.82	$195.80	$195.80
Purchase #7	$17.78	13.796%	$20.2329	$20.23	$20.25	$20.20
7 purchase totals =	$903.85		$1,002.6422	$1,002.64	$1,002.65	$1,002.70