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	$161.61	5.431%	$170.387	$170.39	$170.40	$170.40
Purchase #2	$170.78	11.384%	$190.2216	$190.22	$190.20	$190.20
Purchase #3	$151.28	3.222%	$156.1542	$156.15	$156.15	$156.20
Purchase #4	$99.66	5.818%	$105.4582	$105.46	$105.45	$105.50
Purchase #5	$199.35	3.822%	$206.9692	$206.97	$206.95	$207.00
Purchase #6	$119.76	12.660%	$134.9216	$134.92	$134.90	$134.90
Purchase #7	$61.58	9.726%	$67.5693	$67.57	$67.55	$67.60
7 purchase totals =	$964.02		$1,031.6811	$1,031.68	$1,031.60	$1,031.80