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	$132.47	11.523%	$147.7345	$147.73	$147.75	$147.70
Purchase #2	$25.49	7.850%	$27.491	$27.49	$27.50	$27.50
Purchase #3	$168.64	11.724%	$188.4114	$188.41	$188.40	$188.40
Purchase #4	$42.26	4.552%	$44.1837	$44.18	$44.20	$44.20
Purchase #5	$68.89	11.176%	$76.5891	$76.59	$76.60	$76.60
Purchase #6	$135.95	6.233%	$144.4238	$144.42	$144.40	$144.40
Purchase #7	$34.41	11.179%	$38.2567	$38.26	$38.25	$38.30
7 purchase totals =	$608.11		$667.0902	$667.08	$667.10	$667.10