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	$67.60	12.549%	$76.0831	$76.08	$76.10	$76.10
Purchase #2	$171.87	4.542%	$179.6763	$179.68	$179.70	$179.70
Purchase #3	$82.98	4.614%	$86.8087	$86.81	$86.80	$86.80
Purchase #4	$169.90	5.700%	$179.5843	$179.58	$179.60	$179.60
Purchase #5	$52.86	6.215%	$56.1452	$56.15	$56.15	$56.10
Purchase #6	$10.87	12.541%	$12.2332	$12.23	$12.25	$12.20
Purchase #7	$31.38	13.209%	$35.525	$35.53	$35.55	$35.50
7 purchase totals =	$587.46		$626.0558	$626.06	$626.15	$626.00