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	$151.82	10.231%	$167.3527	$167.35	$167.35	$167.40
Purchase #2	$121.30	5.458%	$127.9206	$127.92	$127.90	$127.90
Purchase #3	$169.99	5.433%	$179.2256	$179.23	$179.25	$179.20
Purchase #4	$234.67	8.827%	$255.3843	$255.38	$255.40	$255.40
Purchase #5	$143.48	12.267%	$161.0807	$161.08	$161.10	$161.10
Purchase #6	$187.92	5.728%	$198.6841	$198.68	$198.70	$198.70
Purchase #7	$132.34	4.194%	$137.8903	$137.89	$137.90	$137.90
7 purchase totals =	$1,141.52		$1,227.5383	$1,227.53	$1,227.60	$1,227.60