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	$229.60	4.435%	$239.7828	$239.78	$239.80	$239.80
Purchase #2	$56.35	6.445%	$59.9818	$59.98	$60.00	$60.00
Purchase #3	$57.90	11.339%	$64.4653	$64.47	$64.45	$64.50
Purchase #4	$126.57	9.581%	$138.6967	$138.70	$138.70	$138.70
Purchase #5	$106.88	7.488%	$114.8832	$114.88	$114.90	$114.90
Purchase #6	$244.39	11.222%	$271.8154	$271.82	$271.80	$271.80
Purchase #7	$209.48	5.812%	$221.655	$221.66	$221.65	$221.70
7 purchase totals =	$1,031.17		$1,111.2802	$1,111.29	$1,111.30	$1,111.40