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	$38.74	12.580%	$43.6135	$43.61	$43.60	$43.60
Purchase #2	$112.62	6.657%	$120.1171	$120.12	$120.10	$120.10
Purchase #3	$225.45	13.470%	$255.8181	$255.82	$255.80	$255.80
Purchase #4	$147.72	4.587%	$154.4959	$154.50	$154.50	$154.50
Purchase #5	$47.38	11.520%	$52.8382	$52.84	$52.85	$52.80
Purchase #6	$228.39	13.839%	$259.9969	$260.00	$260.00	$260.00
Purchase #7	$171.42	10.356%	$189.1723	$189.17	$189.15	$189.20
7 purchase totals =	$971.72		$1,076.0520	$1,076.06	$1,076.00	$1,076.00