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	$41.80	6.695%	$44.5985	$44.60	$44.60	$44.60
Purchase #2	$190.38	3.387%	$196.8282	$196.83	$196.85	$196.80
Purchase #3	$226.54	12.873%	$255.7025	$255.70	$255.70	$255.70
Purchase #4	$167.52	4.476%	$175.0182	$175.02	$175.00	$175.00
Purchase #5	$84.40	8.679%	$91.7251	$91.73	$91.75	$91.70
Purchase #6	$78.47	9.173%	$85.6681	$85.67	$85.65	$85.70
Purchase #7	$144.61	4.367%	$150.9251	$150.93	$150.95	$150.90
7 purchase totals =	$933.72		$1,000.4657	$1,000.48	$1,000.50	$1,000.40