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	$79.70	8.440%	$86.4267	$86.43	$86.45	$86.40
Purchase #2	$112.98	9.293%	$123.4792	$123.48	$123.50	$123.50
Purchase #3	$200.57	13.200%	$227.0452	$227.05	$227.05	$227.00
Purchase #4	$38.87	11.845%	$43.4742	$43.47	$43.45	$43.50
Purchase #5	$79.34	13.607%	$90.1358	$90.14	$90.15	$90.10
Purchase #6	$72.88	5.675%	$77.0159	$77.02	$77.00	$77.00
Purchase #7	$108.43	11.234%	$120.611	$120.61	$120.60	$120.60
7 purchase totals =	$692.77		$768.1880	$768.20	$768.20	$768.10