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	$207.76	10.764%	$230.1233	$230.12	$230.10	$230.10
Purchase #2	$95.87	13.544%	$108.8546	$108.85	$108.85	$108.90
Purchase #3	$99.44	4.444%	$103.8591	$103.86	$103.85	$103.90
Purchase #4	$88.59	6.660%	$94.4901	$94.49	$94.50	$94.50
Purchase #5	$200.43	12.189%	$224.8604	$224.86	$224.85	$224.90
Purchase #6	$221.73	10.212%	$244.3731	$244.37	$244.35	$244.40
Purchase #7	$186.27	5.643%	$196.7812	$196.78	$196.80	$196.80
7 purchase totals =	$1,100.09		$1,203.3418	$1,203.33	$1,203.30	$1,203.50