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	$142.52	9.547%	$156.1264	$156.13	$156.15	$156.10
Purchase #2	$180.92	8.700%	$196.66	$196.66	$196.65	$196.70
Purchase #3	$47.77	4.419%	$49.881	$49.88	$49.90	$49.90
Purchase #4	$68.45	12.547%	$77.0384	$77.04	$77.05	$77.00
Purchase #5	$11.67	10.499%	$12.8952	$12.90	$12.90	$12.90
Purchase #6	$12.83	8.871%	$13.9681	$13.97	$13.95	$14.00
Purchase #7	$238.75	4.236%	$248.8635	$248.86	$248.85	$248.90
7 purchase totals =	$702.91		$755.4326	$755.44	$755.45	$755.50