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	$246.89	4.176%	$257.2001	$257.20	$257.20	$257.20
Purchase #2	$14.92	4.462%	$15.5857	$15.59	$15.60	$15.60
Purchase #3	$35.65	13.806%	$40.5718	$40.57	$40.55	$40.60
Purchase #4	$242.53	11.729%	$270.9763	$270.98	$271.00	$271.00
Purchase #5	$222.52	3.222%	$229.6896	$229.69	$229.70	$229.70
Purchase #6	$36.47	11.210%	$40.5583	$40.56	$40.55	$40.60
Purchase #7	$213.41	13.355%	$241.9109	$241.91	$241.90	$241.90
7 purchase totals =	$1,012.39		$1,096.4927	$1,096.50	$1,096.50	$1,096.60