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	$203.85	7.190%	$218.5068	$218.51	$218.50	$218.50
Purchase #2	$65.44	10.230%	$72.1345	$72.13	$72.15	$72.10
Purchase #3	$47.61	7.169%	$51.0232	$51.02	$51.00	$51.00
Purchase #4	$102.82	8.185%	$111.2358	$111.24	$111.25	$111.20
Purchase #5	$95.87	13.151%	$108.4779	$108.48	$108.50	$108.50
Purchase #6	$53.38	4.758%	$55.9198	$55.92	$55.90	$55.90
Purchase #7	$100.27	8.247%	$108.5393	$108.54	$108.55	$108.50
7 purchase totals =	$669.24		$725.8373	$725.84	$725.85	$725.70