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	$138.57	9.320%	$151.4847	$151.48	$151.50	$151.50
Purchase #2	$190.47	10.658%	$210.7703	$210.77	$210.75	$210.80
Purchase #3	$55.93	6.103%	$59.3434	$59.34	$59.35	$59.30
Purchase #4	$223.47	4.509%	$233.5463	$233.55	$233.55	$233.50
Purchase #5	$94.48	5.830%	$99.9882	$99.99	$100.00	$100.00
Purchase #6	$233.54	11.106%	$259.477	$259.48	$259.50	$259.50
Purchase #7	$61.46	11.290%	$68.3988	$68.40	$68.40	$68.40
7 purchase totals =	$997.92		$1,083.0087	$1,083.01	$1,083.05	$1,083.00