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	$162.93	10.229%	$179.5961	$179.60	$179.60	$179.60
Purchase #2	$30.89	3.194%	$31.8766	$31.88	$31.90	$31.90
Purchase #3	$166.87	9.598%	$182.8862	$182.89	$182.90	$182.90
Purchase #4	$98.82	4.696%	$103.4606	$103.46	$103.45	$103.50
Purchase #5	$20.57	7.615%	$22.1364	$22.14	$22.15	$22.10
Purchase #6	$228.73	7.485%	$245.8504	$245.85	$245.85	$245.90
Purchase #7	$238.27	8.265%	$257.963	$257.96	$257.95	$258.00
7 purchase totals =	$947.08		$1,023.7693	$1,023.78	$1,023.80	$1,023.90