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	$235.27	8.868%	$256.1337	$256.13	$256.15	$256.10
Purchase #2	$205.75	3.849%	$213.6693	$213.67	$213.65	$213.70
Purchase #3	$192.78	12.127%	$216.1584	$216.16	$216.15	$216.20
Purchase #4	$173.34	13.573%	$196.8674	$196.87	$196.85	$196.90
Purchase #5	$50.81	4.440%	$53.066	$53.07	$53.05	$53.10
Purchase #6	$51.92	5.513%	$54.7823	$54.78	$54.80	$54.80
Purchase #7	$40.82	3.217%	$42.1332	$42.13	$42.15	$42.10
7 purchase totals =	$950.69		$1,032.8103	$1,032.81	$1,032.80	$1,032.90