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	$88.55	10.169%	$97.5546	$97.55	$97.55	$97.60
Purchase #2	$181.52	10.186%	$200.0096	$200.01	$200.00	$200.00
Purchase #3	$12.89	12.846%	$14.5458	$14.55	$14.55	$14.50
Purchase #4	$140.28	11.716%	$156.7152	$156.72	$156.70	$156.70
Purchase #5	$126.32	12.723%	$142.3917	$142.39	$142.40	$142.40
Purchase #6	$244.79	3.548%	$253.4751	$253.48	$253.50	$253.50
Purchase #7	$205.66	6.817%	$219.6798	$219.68	$219.70	$219.70
7 purchase totals =	$1,000.01		$1,084.3718	$1,084.38	$1,084.40	$1,084.40