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	$29.60	13.206%	$33.509	$33.51	$33.50	$33.50
Purchase #2	$247.73	13.375%	$280.8639	$280.86	$280.85	$280.90
Purchase #3	$216.54	4.434%	$226.1414	$226.14	$226.15	$226.10
Purchase #4	$82.91	5.678%	$87.6176	$87.62	$87.60	$87.60
Purchase #5	$6.78	13.868%	$7.7203	$7.72	$7.70	$7.70
Purchase #6	$151.85	4.422%	$158.5648	$158.56	$158.55	$158.60
Purchase #7	$209.88	5.766%	$221.9817	$221.98	$222.00	$222.00
7 purchase totals =	$945.29		$1,016.3987	$1,016.39	$1,016.35	$1,016.40