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	$40.40	13.511%	$45.8584	$45.86	$45.85	$45.90
Purchase #2	$110.83	5.398%	$116.8126	$116.81	$116.80	$116.80
Purchase #3	$109.43	12.798%	$123.4349	$123.43	$123.45	$123.40
Purchase #4	$58.92	6.175%	$62.5583	$62.56	$62.55	$62.60
Purchase #5	$79.83	8.869%	$86.9101	$86.91	$86.90	$86.90
Purchase #6	$159.73	7.726%	$172.0707	$172.07	$172.05	$172.10
Purchase #7	$93.40	9.801%	$102.5541	$102.55	$102.55	$102.60
7 purchase totals =	$652.54		$710.1991	$710.19	$710.15	$710.30