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	$120.86	10.854%	$133.9781	$133.98	$134.00	$134.00
Purchase #2	$136.88	4.109%	$142.5044	$142.50	$142.50	$142.50
Purchase #3	$40.53	3.259%	$41.8509	$41.85	$41.85	$41.90
Purchase #4	$31.42	5.341%	$33.0981	$33.10	$33.10	$33.10
Purchase #5	$137.88	3.432%	$142.612	$142.61	$142.60	$142.60
Purchase #6	$153.68	4.320%	$160.319	$160.32	$160.30	$160.30
Purchase #7	$85.68	8.165%	$92.6758	$92.68	$92.70	$92.70
7 purchase totals =	$706.93		$747.0383	$747.04	$747.05	$747.10