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	$39.65	12.393%	$44.5638	$44.56	$44.55	$44.60
Purchase #2	$168.35	10.394%	$185.8483	$185.85	$185.85	$185.80
Purchase #3	$248.89	12.710%	$280.5239	$280.52	$280.50	$280.50
Purchase #4	$33.94	5.787%	$35.9041	$35.90	$35.90	$35.90
Purchase #5	$142.39	7.508%	$153.0806	$153.08	$153.10	$153.10
Purchase #6	$183.52	5.261%	$193.175	$193.18	$193.20	$193.20
Purchase #7	$118.82	8.458%	$128.8698	$128.87	$128.85	$128.90
7 purchase totals =	$935.56		$1,021.9655	$1,021.96	$1,021.95	$1,022.00