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	$112.87	3.806%	$117.1658	$117.17	$117.15	$117.20
Purchase #2	$94.86	6.144%	$100.6882	$100.69	$100.70	$100.70
Purchase #3	$116.91	5.649%	$123.5142	$123.51	$123.50	$123.50
Purchase #4	$127.70	13.592%	$145.057	$145.06	$145.05	$145.10
Purchase #5	$47.27	6.799%	$50.4839	$50.48	$50.50	$50.50
Purchase #6	$163.46	4.845%	$171.3796	$171.38	$171.40	$171.40
Purchase #7	$180.74	11.273%	$201.1148	$201.11	$201.10	$201.10
7 purchase totals =	$843.81		$909.4035	$909.40	$909.40	$909.50