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	$52.82	6.695%	$56.3563	$56.36	$56.35	$56.40
Purchase #2	$175.85	11.743%	$196.5001	$196.50	$196.50	$196.50
Purchase #3	$76.97	4.443%	$80.3898	$80.39	$80.40	$80.40
Purchase #4	$210.74	9.833%	$231.4621	$231.46	$231.45	$231.50
Purchase #5	$102.99	12.681%	$116.0502	$116.05	$116.05	$116.10
Purchase #6	$73.97	6.375%	$78.6856	$78.69	$78.70	$78.70
Purchase #7	$63.26	5.409%	$66.6817	$66.68	$66.70	$66.70
7 purchase totals =	$756.60		$826.1258	$826.13	$826.15	$826.30