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	$69.57	13.315%	$78.8332	$78.83	$78.85	$78.80
Purchase #2	$71.97	9.347%	$78.697	$78.70	$78.70	$78.70
Purchase #3	$78.32	9.624%	$85.8575	$85.86	$85.85	$85.90
Purchase #4	$17.95	6.108%	$19.0464	$19.05	$19.05	$19.00
Purchase #5	$230.56	12.600%	$259.6106	$259.61	$259.60	$259.60
Purchase #6	$41.93	12.284%	$47.0807	$47.08	$47.10	$47.10
Purchase #7	$160.51	7.616%	$172.7344	$172.73	$172.75	$172.70
7 purchase totals =	$670.81		$741.8598	$741.86	$741.90	$741.80