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	$103.94	7.652%	$111.8935	$111.89	$111.90	$111.90
Purchase #2	$79.70	6.831%	$85.1443	$85.14	$85.15	$85.10
Purchase #3	$236.53	5.614%	$249.8088	$249.81	$249.80	$249.80
Purchase #4	$55.62	7.630%	$59.8638	$59.86	$59.85	$59.90
Purchase #5	$94.50	11.451%	$105.3212	$105.32	$105.30	$105.30
Purchase #6	$214.48	8.843%	$233.4465	$233.45	$233.45	$233.40
Purchase #7	$189.32	10.201%	$208.6325	$208.63	$208.65	$208.60
7 purchase totals =	$974.09		$1,054.1106	$1,054.10	$1,054.10	$1,054.00