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	$157.94	5.136%	$166.0518	$166.05	$166.05	$166.10
Purchase #2	$17.27	3.211%	$17.8245	$17.82	$17.80	$17.80
Purchase #3	$200.59	11.437%	$223.5315	$223.53	$223.55	$223.50
Purchase #4	$137.78	4.802%	$144.3962	$144.40	$144.40	$144.40
Purchase #5	$164.75	8.549%	$178.8345	$178.83	$178.85	$178.80
Purchase #6	$220.99	13.409%	$250.6225	$250.62	$250.60	$250.60
Purchase #7	$181.98	4.787%	$190.6914	$190.69	$190.70	$190.70
7 purchase totals =	$1,081.30		$1,171.9524	$1,171.94	$1,171.95	$1,171.90