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	$90.29	5.582%	$95.33	$95.33	$95.35	$95.30
Purchase #2	$97.70	6.216%	$103.773	$103.77	$103.75	$103.80
Purchase #3	$56.50	4.486%	$59.0346	$59.03	$59.05	$59.00
Purchase #4	$10.32	12.544%	$11.6145	$11.61	$11.60	$11.60
Purchase #5	$54.77	8.107%	$59.2102	$59.21	$59.20	$59.20
Purchase #6	$246.49	10.673%	$272.7979	$272.80	$272.80	$272.80
Purchase #7	$132.32	3.555%	$137.024	$137.02	$137.00	$137.00
7 purchase totals =	$688.39		$738.7842	$738.77	$738.75	$738.70