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	$247.87	6.558%	$264.1253	$264.13	$264.15	$264.10
Purchase #2	$205.98	13.376%	$233.5319	$233.53	$233.55	$233.50
Purchase #3	$132.59	3.691%	$137.4839	$137.48	$137.50	$137.50
Purchase #4	$89.25	7.453%	$95.9018	$95.90	$95.90	$95.90
Purchase #5	$68.43	6.461%	$72.8513	$72.85	$72.85	$72.90
Purchase #6	$139.61	10.749%	$154.6167	$154.62	$154.60	$154.60
Purchase #7	$129.95	13.497%	$147.4894	$147.49	$147.50	$147.50
7 purchase totals =	$1,013.68		$1,106.0003	$1,106.00	$1,106.05	$1,106.00