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	$153.77	8.264%	$166.4776	$166.48	$166.50	$166.50
Purchase #2	$27.25	8.283%	$29.5071	$29.51	$29.50	$29.50
Purchase #3	$143.25	13.684%	$162.8523	$162.85	$162.85	$162.90
Purchase #4	$183.93	6.181%	$195.2987	$195.30	$195.30	$195.30
Purchase #5	$80.42	13.521%	$91.2936	$91.29	$91.30	$91.30
Purchase #6	$171.87	11.190%	$191.1023	$191.10	$191.10	$191.10
Purchase #7	$185.70	3.161%	$191.57	$191.57	$191.55	$191.60
7 purchase totals =	$946.19		$1,028.1016	$1,028.10	$1,028.10	$1,028.20