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	$119.50	7.545%	$128.5163	$128.52	$128.50	$128.50
Purchase #2	$139.89	6.751%	$149.334	$149.33	$149.35	$149.30
Purchase #3	$54.29	11.856%	$60.7266	$60.73	$60.75	$60.70
Purchase #4	$46.43	10.129%	$51.1329	$51.13	$51.15	$51.10
Purchase #5	$134.31	7.606%	$144.5256	$144.53	$144.55	$144.50
Purchase #6	$95.52	4.785%	$100.0906	$100.09	$100.10	$100.10
Purchase #7	$122.89	9.238%	$134.2426	$134.24	$134.25	$134.20
7 purchase totals =	$712.83		$768.5686	$768.57	$768.65	$768.40