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	$108.95	9.774%	$119.5988	$119.60	$119.60	$119.60
Purchase #2	$84.59	12.199%	$94.9091	$94.91	$94.90	$94.90
Purchase #3	$13.82	9.194%	$15.0906	$15.09	$15.10	$15.10
Purchase #4	$29.79	12.627%	$33.5516	$33.55	$33.55	$33.60
Purchase #5	$173.68	13.163%	$196.5415	$196.54	$196.55	$196.50
Purchase #6	$164.32	6.111%	$174.3616	$174.36	$174.35	$174.40
Purchase #7	$212.25	6.551%	$226.1545	$226.15	$226.15	$226.20
7 purchase totals =	$787.40		$860.2077	$860.20	$860.20	$860.30