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	$105.35	13.236%	$119.2941	$119.29	$119.30	$119.30
Purchase #2	$106.28	11.225%	$118.2099	$118.21	$118.20	$118.20
Purchase #3	$67.91	5.116%	$71.3843	$71.38	$71.40	$71.40
Purchase #4	$54.39	13.716%	$61.8501	$61.85	$61.85	$61.90
Purchase #5	$5.27	10.171%	$5.806	$5.81	$5.80	$5.80
Purchase #6	$100.71	13.782%	$114.5899	$114.59	$114.60	$114.60
Purchase #7	$94.42	8.867%	$102.7922	$102.79	$102.80	$102.80
7 purchase totals =	$534.33		$593.9265	$593.92	$593.95	$594.00