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	$174.66	3.604%	$180.9547	$180.95	$180.95	$181.00
Purchase #2	$158.65	7.576%	$170.6693	$170.67	$170.65	$170.70
Purchase #3	$29.35	7.293%	$31.4905	$31.49	$31.50	$31.50
Purchase #4	$172.48	4.634%	$180.4727	$180.47	$180.45	$180.50
Purchase #5	$215.74	12.553%	$242.8218	$242.82	$242.80	$242.80
Purchase #6	$140.41	9.326%	$153.5046	$153.50	$153.50	$153.50
Purchase #7	$53.73	4.730%	$56.2714	$56.27	$56.25	$56.30
7 purchase totals =	$945.02		$1,016.1850	$1,016.17	$1,016.10	$1,016.30