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	$94.66	8.826%	$103.0147	$103.01	$103.00	$103.00
Purchase #2	$168.68	9.468%	$184.6506	$184.65	$184.65	$184.70
Purchase #3	$171.46	5.463%	$180.8269	$180.83	$180.85	$180.80
Purchase #4	$153.70	11.584%	$171.5046	$171.50	$171.50	$171.50
Purchase #5	$117.46	13.149%	$132.9048	$132.90	$132.90	$132.90
Purchase #6	$151.56	11.778%	$169.4107	$169.41	$169.40	$169.40
Purchase #7	$187.84	10.669%	$207.8806	$207.88	$207.90	$207.90
7 purchase totals =	$1,045.36		$1,150.1929	$1,150.18	$1,150.20	$1,150.20