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	$43.69	3.349%	$45.1532	$45.15	$45.15	$45.20
Purchase #2	$91.38	4.615%	$95.5972	$95.60	$95.60	$95.60
Purchase #3	$98.83	9.735%	$108.4511	$108.45	$108.45	$108.50
Purchase #4	$104.50	10.813%	$115.7996	$115.80	$115.80	$115.80
Purchase #5	$49.75	10.583%	$55.015	$55.02	$55.00	$55.00
Purchase #6	$46.50	5.596%	$49.1021	$49.10	$49.10	$49.10
Purchase #7	$237.96	7.831%	$256.5946	$256.59	$256.60	$256.60
7 purchase totals =	$672.61		$725.7128	$725.71	$725.70	$725.80