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	$68.50	4.690%	$71.7127	$71.71	$71.70	$71.70
Purchase #2	$193.35	6.618%	$206.1459	$206.15	$206.15	$206.10
Purchase #3	$149.50	7.136%	$160.1683	$160.17	$160.15	$160.20
Purchase #4	$94.41	13.694%	$107.3385	$107.34	$107.35	$107.30
Purchase #5	$177.59	10.874%	$196.9011	$196.90	$196.90	$196.90
Purchase #6	$92.44	8.725%	$100.5054	$100.51	$100.50	$100.50
Purchase #7	$97.27	5.554%	$102.6724	$102.67	$102.65	$102.70
7 purchase totals =	$873.06		$945.4443	$945.45	$945.40	$945.40