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	$74.57	10.823%	$82.6407	$82.64	$82.65	$82.60
Purchase #2	$119.75	11.265%	$133.2398	$133.24	$133.25	$133.20
Purchase #3	$238.67	7.132%	$255.6919	$255.69	$255.70	$255.70
Purchase #4	$105.73	13.579%	$120.0871	$120.09	$120.10	$120.10
Purchase #5	$175.52	6.554%	$187.0236	$187.02	$187.00	$187.00
Purchase #6	$27.41	13.843%	$31.2044	$31.20	$31.20	$31.20
Purchase #7	$98.47	7.116%	$105.4771	$105.48	$105.50	$105.50
7 purchase totals =	$840.12		$915.3646	$915.36	$915.40	$915.30