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	$163.67	5.817%	$173.1907	$173.19	$173.20	$173.20
Purchase #2	$149.95	13.300%	$169.8934	$169.89	$169.90	$169.90
Purchase #3	$243.83	13.802%	$277.4834	$277.48	$277.50	$277.50
Purchase #4	$182.86	11.724%	$204.2985	$204.30	$204.30	$204.30
Purchase #5	$40.27	3.500%	$41.6795	$41.68	$41.70	$41.70
Purchase #6	$195.97	7.375%	$210.4228	$210.42	$210.40	$210.40
Purchase #7	$104.97	13.624%	$119.2711	$119.27	$119.25	$119.30
7 purchase totals =	$1,081.52		$1,196.2394	$1,196.23	$1,196.25	$1,196.30