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	$216.68	5.641%	$228.9029	$228.90	$228.90	$228.90
Purchase #2	$43.91	8.137%	$47.483	$47.48	$47.50	$47.50
Purchase #3	$249.30	12.665%	$280.8738	$280.87	$280.85	$280.90
Purchase #4	$151.60	11.263%	$168.6747	$168.67	$168.65	$168.70
Purchase #5	$171.34	8.773%	$186.3717	$186.37	$186.35	$186.40
Purchase #6	$166.69	4.453%	$174.1127	$174.11	$174.10	$174.10
Purchase #7	$49.60	11.718%	$55.4121	$55.41	$55.40	$55.40
7 purchase totals =	$1,049.12		$1,141.8309	$1,141.81	$1,141.75	$1,141.90