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	$211.92	7.504%	$227.8225	$227.82	$227.80	$227.80
Purchase #2	$89.68	12.135%	$100.5627	$100.56	$100.55	$100.60
Purchase #3	$114.30	5.435%	$120.5122	$120.51	$120.50	$120.50
Purchase #4	$146.29	9.589%	$160.3177	$160.32	$160.30	$160.30
Purchase #5	$166.45	12.861%	$187.8571	$187.86	$187.85	$187.90
Purchase #6	$213.77	9.339%	$233.734	$233.73	$233.75	$233.70
Purchase #7	$52.52	5.851%	$55.5929	$55.59	$55.60	$55.60
7 purchase totals =	$994.93		$1,086.3991	$1,086.39	$1,086.35	$1,086.40