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	$82.74	8.439%	$89.7224	$89.72	$89.70	$89.70
Purchase #2	$230.93	5.616%	$243.899	$243.90	$243.90	$243.90
Purchase #3	$122.98	13.332%	$139.3757	$139.38	$139.40	$139.40
Purchase #4	$85.90	12.829%	$96.9201	$96.92	$96.90	$96.90
Purchase #5	$226.81	12.754%	$255.7373	$255.74	$255.75	$255.70
Purchase #6	$50.67	10.509%	$55.9949	$55.99	$56.00	$56.00
Purchase #7	$207.91	3.150%	$214.4592	$214.46	$214.45	$214.50
7 purchase totals =	$1,007.94		$1,096.1086	$1,096.11	$1,096.10	$1,096.10