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	$143.31	6.689%	$152.896	$152.90	$152.90	$152.90
Purchase #2	$54.45	9.242%	$59.4823	$59.48	$59.50	$59.50
Purchase #3	$16.98	9.264%	$18.553	$18.55	$18.55	$18.60
Purchase #4	$51.81	6.293%	$55.0704	$55.07	$55.05	$55.10
Purchase #5	$82.57	9.800%	$90.6619	$90.66	$90.65	$90.70
Purchase #6	$134.83	8.291%	$146.0088	$146.01	$146.00	$146.00
Purchase #7	$158.93	8.867%	$173.0223	$173.02	$173.00	$173.00
7 purchase totals =	$642.88		$695.6947	$695.69	$695.65	$695.80