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	$239.32	13.558%	$271.767	$271.77	$271.75	$271.80
Purchase #2	$118.91	11.808%	$132.9509	$132.95	$132.95	$133.00
Purchase #3	$161.86	4.806%	$169.639	$169.64	$169.65	$169.60
Purchase #4	$52.41	4.182%	$54.6018	$54.60	$54.60	$54.60
Purchase #5	$57.32	4.396%	$59.8398	$59.84	$59.85	$59.80
Purchase #6	$196.49	6.501%	$209.2638	$209.26	$209.25	$209.30
Purchase #7	$102.78	11.316%	$114.4106	$114.41	$114.40	$114.40
7 purchase totals =	$929.09		$1,012.4729	$1,012.47	$1,012.45	$1,012.50