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	$118.56	7.304%	$127.2196	$127.22	$127.20	$127.20
Purchase #2	$118.57	12.518%	$133.4126	$133.41	$133.40	$133.40
Purchase #3	$169.82	5.377%	$178.9512	$178.95	$178.95	$179.00
Purchase #4	$13.52	11.536%	$15.0797	$15.08	$15.10	$15.10
Purchase #5	$132.96	11.103%	$147.7225	$147.72	$147.70	$147.70
Purchase #6	$98.46	11.361%	$109.646	$109.65	$109.65	$109.60
Purchase #7	$184.87	6.526%	$196.9346	$196.93	$196.95	$196.90
7 purchase totals =	$836.76		$908.9662	$908.96	$908.95	$908.90