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	$152.73	5.458%	$161.066	$161.07	$161.05	$161.10
Purchase #2	$245.68	8.513%	$266.5947	$266.59	$266.60	$266.60
Purchase #3	$76.44	5.445%	$80.6022	$80.60	$80.60	$80.60
Purchase #4	$56.97	4.383%	$59.467	$59.47	$59.45	$59.50
Purchase #5	$61.81	9.328%	$67.5756	$67.58	$67.60	$67.60
Purchase #6	$129.66	11.781%	$144.9352	$144.94	$144.95	$144.90
Purchase #7	$6.65	11.544%	$7.4177	$7.42	$7.40	$7.40
7 purchase totals =	$729.94		$787.6584	$787.67	$787.65	$787.70