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	$221.38	11.323%	$246.4469	$246.45	$246.45	$246.40
Purchase #2	$137.38	9.480%	$150.4036	$150.40	$150.40	$150.40
Purchase #3	$194.41	12.528%	$218.7657	$218.77	$218.75	$218.80
Purchase #4	$98.85	4.830%	$103.6245	$103.62	$103.60	$103.60
Purchase #5	$209.85	5.427%	$221.2386	$221.24	$221.25	$221.20
Purchase #6	$80.83	12.301%	$90.7729	$90.77	$90.75	$90.80
Purchase #7	$235.49	12.179%	$264.1703	$264.17	$264.15	$264.20
7 purchase totals =	$1,178.19		$1,295.4225	$1,295.42	$1,295.35	$1,295.40