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	$214.40	11.311%	$238.6508	$238.65	$238.65	$238.70
Purchase #2	$173.45	8.865%	$188.8263	$188.83	$188.85	$188.80
Purchase #3	$146.36	13.427%	$166.0118	$166.01	$166.00	$166.00
Purchase #4	$160.41	6.671%	$171.111	$171.11	$171.10	$171.10
Purchase #5	$47.29	12.285%	$53.0996	$53.10	$53.10	$53.10
Purchase #6	$29.31	7.440%	$31.4907	$31.49	$31.50	$31.50
Purchase #7	$208.51	7.776%	$224.7237	$224.72	$224.70	$224.70
7 purchase totals =	$979.73		$1,073.9139	$1,073.91	$1,073.90	$1,073.90