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	$67.68	7.678%	$72.8765	$72.88	$72.90	$72.90
Purchase #2	$144.28	8.194%	$156.1023	$156.10	$156.10	$156.10
Purchase #3	$116.58	11.581%	$130.0811	$130.08	$130.10	$130.10
Purchase #4	$176.87	5.688%	$186.9304	$186.93	$186.95	$186.90
Purchase #5	$98.86	3.791%	$102.6078	$102.61	$102.60	$102.60
Purchase #6	$37.29	8.281%	$40.378	$40.38	$40.40	$40.40
Purchase #7	$20.28	4.420%	$21.1764	$21.18	$21.20	$21.20
7 purchase totals =	$661.84		$710.1525	$710.16	$710.25	$710.20