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	$213.64	4.371%	$222.9782	$222.98	$223.00	$223.00
Purchase #2	$63.47	13.576%	$72.0867	$72.09	$72.10	$72.10
Purchase #3	$47.86	6.799%	$51.114	$51.11	$51.10	$51.10
Purchase #4	$227.57	4.785%	$238.4592	$238.46	$238.45	$238.50
Purchase #5	$87.79	5.868%	$92.9415	$92.94	$92.95	$92.90
Purchase #6	$165.94	5.388%	$174.8808	$174.88	$174.90	$174.90
Purchase #7	$56.80	5.149%	$59.7246	$59.72	$59.70	$59.70
7 purchase totals =	$863.07		$912.1850	$912.18	$912.20	$912.20