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	$161.94	8.871%	$176.3057	$176.31	$176.30	$176.30
Purchase #2	$38.39	6.607%	$40.9264	$40.93	$40.95	$40.90
Purchase #3	$237.54	9.651%	$260.465	$260.47	$260.45	$260.50
Purchase #4	$20.71	4.132%	$21.5657	$21.57	$21.55	$21.60
Purchase #5	$47.86	12.405%	$53.797	$53.80	$53.80	$53.80
Purchase #6	$41.42	5.163%	$43.5585	$43.56	$43.55	$43.60
Purchase #7	$115.94	10.181%	$127.7439	$127.74	$127.75	$127.70
7 purchase totals =	$663.80		$724.3622	$724.38	$724.35	$724.40