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	$54.46	11.552%	$60.7512	$60.75	$60.75	$60.80
Purchase #2	$127.25	9.567%	$139.424	$139.42	$139.40	$139.40
Purchase #3	$45.76	10.139%	$50.3996	$50.40	$50.40	$50.40
Purchase #4	$158.44	8.223%	$171.4685	$171.47	$171.45	$171.50
Purchase #5	$138.83	3.646%	$143.8917	$143.89	$143.90	$143.90
Purchase #6	$132.86	12.103%	$148.94	$148.94	$148.95	$148.90
Purchase #7	$250.47	3.631%	$259.5646	$259.56	$259.55	$259.60
7 purchase totals =	$908.07		$974.4396	$974.43	$974.40	$974.50